Abstract: During the operation or stop of a vertical hydrogenerator unit, water accumulation may occur on the head cover of the turbine. If the water accumulation on the head cover exceeds the safe water level, it can cause accidents and endanger the safe operation of the unit. Therefore, when the water level exceeds a certain limit, a drainage pump should be used to timely discharge the water accumulation on the head cover. In the head cover drainage system, a float switch is used to monitor the accumulated water level on the head cover, and the water level switch signal is sent to the drainage pump control PLC. The PLC controls the start and stop of the drainage pump by controlling the drive circuit of the drainage pump, ensuring that the accumulated water level is always within the safe threshold and achieving automatic control to ensure the safe and stable operation of the unit. This article introduces the control design method of the combined head cover drainage system with three drainage pumps from the perspectives of electrical and control, this method improves the overall efficiency and reliability of the head cover drainage system，achieving system optimization.