A, site selection ① ground open, flat; ② try to choose the wind zone; ③ near the water, irrigation and drainage is convenient; ④ non-polluting, non-saline plots; ⑤ from the residential areas and highways, power supply, etc. closer to the place of greenhouse mainly sunlight as an energy source, almost no heating or less heating can be carried out in the winter crop production, but the greenhouse crops in the growing period is the weakest season of solar radiation, whether it can be sufficiently Reasonably benefit from the sun's radiation crops, related to the success or failure of greenhouse production. Greenhouse to maintain a high temperature during the day is conducive to the growth of crops, the low temperature at night is a direct threat to the plant. Construction precautions greenhouse should be taken in principle east and west extension, sitting north to south orientation. This is conducive to receiving more solar radiation in winter. Appropriate eastward shift to the south can appropriately increase the light intensity in the morning indoors; appropriate westward shift to the south can increase the light intensity in the afternoon. Favorable to increase the indoor temperature at night. However, the winter greenhouse see light how much is also affected by the uncovering of the quilt morning and evening. In winter, low temperatures, morning fog in the region, the morning quilt uncovering time is late, so the orientation of the south east is not suitable. According to the experience of the north, the orientation of the greenhouse to determine the focus on improving nighttime temperatures, so the greenhouse to take a slightly west of 5 to 8 degrees to the south of the orientation is good. The modulation of greenhouse orientation can be determined by instruments such as azimuth meter, can also be used to determine the light and shadow of the noon time. The latter method does not require any instrumentation, only with the help of bamboo poles, ropes, rulers can complete the adjustment of the orientation. Construction precautions 1, in the greenhouse without columns of the back wall and the front foot of the arch foundation to withstand a large horizontal thrust, brick wall masonry mortar strength is not enough will lead to the destruction of the back wall and the front foot of the foundation of the arch, the bridge arch foot displacement, the entire bearing capacity of the bridge frame will be greatly reduced, or even loss of bearing capacity. Therefore, the construction must strictly control the strength of masonry mortar. 2,) light steel bridge chord should be used as far as possible through the length of the steel, the length of the upper chord fittings is not enough, should be used to weld the connection, the connection point should be avoided tensile region, generally will be connected to the chord of the front of the slope of the total length of the arrangement of the point above the bisecting the front slope of the shoulder of the chord culm is not allowed to welding. Bridge transverse support lap can be used casing bolt coupling method. 3, the selection of polystyrene foam board (hereinafter referred to as benzene board) for the wall or rear roof insulation material, its capacity should not be less than 2Okg/m3. capacity is too small, the construction process of the plate is easy to fall off the corner or broken. 4, the use of welded steel frame, all the roof steel components should be strictly de-rusting. And brush antirust paint two times. In the process of use, rust should be removed and anti-rust paint should be brushed every year. Otherwise, its service life will be affected.