Three major controls are usually emphasized in the implementation of engineering projects: quality control, time limit control and cost control. Cost control is one of the important links. The effect of cost control is not only related to the successful completion of the project, but also directly affects the economic benefits of construction enterprises. The author tries to explain the application of several cost control methods from the perspective of the whole process of project management in construction enterprises. Application of 1 regression method in cost prediction of construction projects. Cost forecasting refers to judging and speculating the cost by using the methods of experience summary, statistical analysis and mathematical model through the historical digital data obtained. Through the project construction cost forecast, it can provide the basis for the management decision of construction enterprises and the preparation of cost plan by the project department. Cost prediction is the basis of bidding decision, the basis of cost planning and an important link of cost management. Construction units often estimate the project cost according to past experience, which is actually a prediction, and its role cannot be underestimated. However, in order to predict the construction cost more accurately and effectively, it is difficult to do it only by empirical estimation. Only by using scientific and systematic forecasting methods can forecasting play a greater role in project management and operation. In project cost forecasting, regression forecasting method is often used. The so-called regression analysis method is a mathematical statistical method to analyze the relationship between related factors. By establishing a regression analysis model of one or a group of independent variables and related random variables, the future value of related random variables is predicted [1]. According to the relationship between labor cost and construction output value in highway construction, the annual labor cost of highway construction is predicted by regression analysis. Labor cost can be obtained by predicting the number of working days of the road and multiplying it by the unit price of labor cost. 1) Collect the construction output value and man-days in recent 10 years, with the annual construction output value as the independent variable X and the man-days as the dependent variable Y (see table 1). The linear regression model Y=a+bX is established, and then the regression coefficients a and b are obtained by using the principle of ordinary least square method. Using the data in table 1, we can get the following results: 2) Find a suitable mathematical equation (i.e. regression model) Y=- 1 147+4.2X to describe the relationship between variables. Because the variables involved are uncertain, it is necessary to test the regression model statistically. 3) After the statistical test is passed, the predicted dependent variable is estimated by regression model according to the explanatory variable. It is estimated that the output value of highway construction in 2006 is 22.37 million yuan. If y =-147+4.2x and y = 8,248 man-days, the predicted annual labor cost of highway construction is: 45 yuan/man-days-8,248 = 3,768. 2 The application of four-calculation comparative analysis method in the cost analysis of construction projects. It is very important to master the appropriate analysis method for cost management. Only by mastering the appropriate analysis methods can we find out the cost management problems in time and find out the reasons, so as to prescribe the right medicine. Four-calculation comparative analysis method is one of the effective methods for cost analysis of construction projects. The first calculation: calculating the contract budget, also called the bid-winning estimate, is the income basis of the project. The second calculation: the construction budget, also known as the contract budget, is prepared by the company according to the construction quota, and the company with enterprise quota is prepared according to the enterprise quota, which will be used as the control limit of the project department. The project department must control the occurrence of various expenses within the budget during the construction process. In addition, according to the actual situation, the construction budget plays different roles in different situations. When solving the problem of rapid cost estimation of contract plan, the second is the concept of contract budget, which plays a role in replacing construction plan; When solving the budget revenue problem of trilateral project, the concept of secondary calculation is construction budget, which plays a role in replacing the bid-winning budget. The third calculation: the calculated planned cost is the cost summarized according to the plan guiding the construction, and it is the estimation and control index of the actual construction cost before and during the construction. In the process of compiling, it should be emphasized not to break through the construction budget. If the actual situation cannot be realized, it will be strictly controlled within the winning bid budget. The fourth calculation: calculating the actual cost is the collection of actual consumption and represents the actual consumption level. In the process of actual cost, we should always compare it with the planned cost, and use the planned cost to assess the actual cost. After the actual cost occurs, it should be recorded in time to ensure that the cost information is comprehensive, complete and true. Four calculation relationships of project cost are shown in figure 1. The analysis method of construction project cost is basically the same as that of general problems, and should follow the principle of comparative analysis, from macro to micro, from comprehensive to key, from coarse to fine, from outside to inside. The conclusion of the analysis is obtained through data comparison, so data comparison is the basic principle of analysis. Comparative analysis should grasp two basic constraints: one is benchmark comparison, and the other is content comparison. The uses and contents of several commonly used analysis tables in construction cost management are shown in Table 2. In the analysis, we should follow the analysis method from coarse to fine, from the surface to the inside: 1) summarize the cost analysis table, and look at the difference between the budgeted income and the actual cost of the whole project from the perspective of cost composition. 2) Pay attention to loss expense items, focus on large cost items, and investigate the causes of profit and loss one by one. The main cost items include: profit and loss of subcontracting expenses, profit and loss of reinforcement expenses, profit and loss of commercial concrete expenses, profit and loss of turnover materials expenses, profit and loss of machinery use fees and profit and loss of temporary facilities expenses. 3) For projects with large losses, volume and price analysis is generally done first. See Figure 2 for details. In short, in the project cost analysis, we mainly consider the comparative analysis of four data, namely, the winning bid budget, the construction budget, the planned cost and the actual cost. At the same time, from the perspective of volume and price analysis, such cost analysis results are valuable and more convincing. 3 Application of value engineering method in cost control of construction projects Value engineering is a management technology aiming at improving the value of products or operations, and through organized creative work, it is required to reliably realize the functions required by users at the lowest life cycle cost [2]. Therefore, the application of value engineering should not only study technology, but also study economy, that is, improve the function without increasing the cost, or reduce the cost without affecting the function, and unify the improved function and reduced cost in the best scheme. The purpose of value engineering is to make products or operations have appropriate value at the lowest cost, that is, to realize their necessary functions. Therefore, the relationship among value, function and cost can be inspired, and producers and operators of products can improve the value of products or operations in the following five ways: reducing costs while improving the functional level; Improve the function level while keeping the cost unchanged, and reduce the cost while keeping the function level unchanged; The cost is slightly increased, but the functional level is greatly improved; The function level is slightly reduced, but the cost is greatly reduced [3]. From these aspects, it can be seen that in the process of project construction, while analyzing the engineering structure and construction conditions, the construction scheme and its functions of the project construction should be decomposed to determine the lowest cost scheme to realize the construction scheme and its functions. In the construction of Yongding River Bridge in Lianhuachi West Road Project, we used the method of value engineering to calculate and compare whether the bridge adopts steel-wood composite formwork or small steel formwork system. The specific application is as follows: 1) Determine the analysis object and task. The cast-in-place concrete construction of this bridge plans to adopt steel-wood composite formwork system or small steel formwork system. After discussion by relevant personnel of the project department, it is decided to evaluate the two schemes from five technical and economic indicators: total amortization cost of formwork (F 1), quality of cast-in-place concrete (F2), labor cost of formwork (F3), turnover time of formwork (F4) and convenience of dismantling formwork (F5), and 0 is adopted. 2) Calculate the function coefficient. Firstly, determine the function proportion coefficient, that is, determine the proportion of each function in the project according to the function of the above functions in the division project, and modify the function proportion to calculate the weight of each technical and economic index (see Table 3 [2]); Finally, calculate the function coefficient (see Table 4). 3) Calculate the cost coefficient and value coefficient. ① Calculate the cost coefficient of the project, that is, the proportion of the budgeted cost of the project to the total budgeted cost. According to the cost engineer's estimation, the total amortization cost of steel-wood composite formwork in this project is 420,000 yuan, and the labor cost of cast-in-place concrete formwork is 8.5 yuan/m2; The total amortization cost of small steel formwork in this project is 530,000 yuan, and the labor cost of cast-in-place concrete formwork is 5.5 yuan /m2. The total number of templates is 23,000m2. The cost of steel-wood composite formwork is 42/2.3+8.5=26.76 yuan /m2, and the cost index of steel-wood composite formwork is 26.76/(26.76+28.54)=0.48. The single formwork cost of small steel formwork is 53/2.3+5.5=28.54 yuan /m2, and the cost index of small steel formwork is 28.54/(26.76+28.54)=0.52. ② Calculate the value coefficient of the project. Value coefficient of steel-wood composite formwork: 0.513/0.48 =10.07, and value coefficient of small steel formwork: 0.487/0.52=0.94. 4) Analysis, diagnosis and improvement of construction scheme. Through the calculation of the above functional coefficient, cost coefficient and value coefficient, the scheme itself can be judged according to the value coefficient of the project. When the value coefficient is less than 1, the cost of the scheme is greater than the function, and the original construction scheme needs to be improved. On the contrary, when the value coefficient is greater than 1, the function of the scheme is greater than the cost, so it is judged that the scheme is satisfactory and can be operated according to the construction scheme. According to the above calculation results and standards, the value coefficient of steel-wood composite formwork is higher than that of small steel formwork, so the steel-wood composite formwork system should be selected. However, it should be noted that whether the construction scheme is reasonable and advanced requires the project manager to convene relevant engineering and technical personnel and economic management personnel for consultation, diagnose the crux of the problem, and formulate effective measures to solve the problem, so as to improve the use value of the project from improving functions or reducing costs.

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