The size of Wan’an second-line lock’s chamber is large and its hydraulic head is relatively high. Besides，its water level variation and hydraulic index requirements have reached the forefront of the single-stage locks built in the world，therefore the cavitation and vibration of valve section will be more prominent if no effective optimizations are taken. Based on a constant flow pressure reduction model test of the valve，we observe the valve section cavitation behavior and calculate the critical cavitation number. According to the characteristics of valve section，a combined ventilation method （valve lintel natural ventilation +drop-sill forced ventilation） is put forward to improve the valve cavitation condition，which can solve the problem of valve cavitation of Wan’an second-line lock with a hydraulic head of 32.5 m.