Abstract: At present, due to the long construction period of some old residential areas, the reliability, stability and processing capacity of their drainage control systems have been unable to meet the current usage requirements. In response to this, this paper designs a drainage control system with PLC controllers and frequency converters as the core components. Through the optimization of hardware selection and software program design, the drainage processing efficiency of old residential areas is effectively improved, providing a practical solution for the transformation of drainage systems in old residential areas.