The layout of “parallel three valves+rectangular sudden expansion” is adopted in the valve section of Jinghong hydro-drvien ship lift. At present, there is no scientific guiding basis for the flow distribution of the combined valves. In this paper, based on Jinghong hydro-drvien ship lift, a three-dimensional numerical model of valve segment is built to study the flow field characteristics under different flow ratios of combined valves. The results show that the flow field uniformity of joint operation of three valves is the best. When the flow ratio of valves is equal to 31, the lowest pressure in the flow field is the highest, the maximum velocity is the lowest, the turbulence is weak, and the cavitation is best inhibited. The reasonable flow ratio of combined valves is positively correlated with the flow coefficient ratio. The optimal flow ratio of the main and auxiliary valves is approximately equal to 3:1 for combined valves in Jinghong project.