In the study of automation technology of 50 000 t/d Jinqiao Sewage Plant, optical fiber transmission and EtherNet communication mode were adopted to realize network communication of central control rooms and 2 PLC stations, with simple structure and high stability. PLC with remote I/O station, with communication PROFIBUS-DP, Baud rate 187.5bps, balancing data volume and data transmission speed. Based on the water inflow research of the plant, A2O was adopted, information technology +PLC+ smart meter + frequency conversion technology enabled to automatic control and real-time data transmission of sewage treatment.