Abstract: In order to solve problem of high cost of running management of relay-contactor control mode commonly used in sewage pumping station at present, the paper proposed a design scheme of automatic control system for sewage pumping station which takes S7-300 PLC as core, introduced the system's composition and control principle, and expounded design of the system's hardware and software. The system uses PLC to control a soft-starter to drive four motors, so as to eliminate influence on motors caused by direct starting. Besides, the system can automatically choose the most reasonable running state according to different situations, and communicate with upper computer to upload data and receive control orders. The practical application showed that the system is stable in running and improves water purifying efficiency of sewage pumping station.