With the development of, the pressure of urban water shortage is increasing. Investigating the root cause of urban water crisis, people increasingly realize that the social circulation of water is beyond the bearing range of natural circulation of water. Therefore, only by fully respecting the natural movement law of water, rationally using water resources, so that the water circulation in the upper reaches does not affect the water function in the lower waters, and the social circulation does not damage the objective law of natural circulation, so as to maintain or restore the good water environment in cities and even river basins, is the effective way of sustainable utilization of water resources. This requires us to change from the one-way open water use mode of "water intake-water delivery-user-discharge" to the feedback circulation process of "water intake-water delivery-user-reclaimed water" to improve water utilization efficiency. To realize this major change in water use mode, strengthening sewage recycling is the key. With the progress of science and technology, urban sewage is no longer wastewater, but a valuable resource. Since it is a kind of resource, we should make the best use of it. Improving the recycling rate of urban sewage can reduce pollutant discharge and save limited water resources. Cheng Xiaobing, deputy director of the Water Resources Department of the Ministry of Water Resources, delivered a speech at the "2111 Urban Water Strategy Forum" sponsored by Tsinghua University and China Water Network. He pointed out that China is short of water resources, and the problem of urban water shortage is prominent. Sewage treatment and reuse is a strategic choice and of great significance. Urban sewage treatment and reuse can replace clean water source, reduce sewage discharge and urban sewage load, and has the characteristics of stable water quantity, short water delivery distance and low water production cost. It can provide safe and reliable alternative water source and is a strategic choice to solve the problem of urban water shortage. Promoting sewage treatment and reuse fully reflects the people-oriented requirements of Scientific Outlook on Development, reflects the urgent desire of the broad masses of people, is an objective need to promote urbanization, is an important means to realize rational allocation, scientific protection and recycling of water resources, and is of great significance to building a resource-saving and environment-friendly society and to the sound and rapid development of China's economy.