Abstract: The existing water ring vacuum pump has low working efficiency and cannot describe the flow law of the internal flow field intuitively and accurately, which greatly limits the development and application of new water ring pumps. In order to solve the above problems, this paper based on the FLUENT software to simulate the flow field of the water ring pump, explore the distribution law of gas-liquid state, pressure and velocity vector in the pump; compare the suction volume with the manufacturer's test results to verify the accuracy of the simulation results; on this basis, analyze the effect of radial clearance and the number of blades on suction. The optimal parameter combination of radial clearance and number of blades is determined by considering the influence of volume,shaft power and gas isothermal compression efficiency. The numerical simulation results show that the optimal parameter combination is the radial clearance of 25 mm and the number of blades of 17. At this time, the suction capacity of the pump is increased by 7%, and the working performance of the water ring vacuum pump is optimized,which provides theoretical support for the design of the water ring pump in the future and improves the research and development efficiency.