Abstract: ABSRTACT: The 660MW unit circulating water pump butterfly valve control system of a power plant originally adopted the local PLC control cabinet mode, the relevant logic and signal of the butterfly valve were in the PLC, and the host DCS screen could only monitor the butterfly valve status and send switch instructions remotely. This article describes the whole process of the PLC logic and control loop analysis by the thermal engineers of the power plant, canceling the PLC, integrating the relevant logic configuration into the host DCS, rebuilding the control cabinet hard wiring loop, and optimizing the control cabinet power supply.