With socioeconomic development and rapid urbanization, the water shortage due to contamination of water quality becomes more and more severe in Yangtze River Basin. So, the authors introduces the present situation of city sewage treatment and analyze the water saving effect of city sewage treatment. Finally, two kinds of water saving measures are concluded as follows: One is to enhance urban sewage treatment rate by building more sewage drainage works to solve the problem of water shortage owing to water pollution；the other is to upgrade reuse rate by adopting advanced city sewage treatment plant to save valuable fresh water resources.