The initial period rainwater has a great influence on the quality of surface water in Tianjin city. To reducing the initial period rainwater pollution, the effective control measures must be taken for initial period rainwater. A comprehensive operation regulation by using the surplus capacity of sewage treatment plant, reservoirs and rivers is proposed and studied in this paper. The order of initial period rainwater storage is firstly in sewage treatment plant, then in reservoirs and finally drainage to rivers. By carefully arranging the intercepted amount of every storage stage, the pollution of initial period rainfall in an example Tianjin area is shown to be effectively solved.