Abstract: Existing large liquid ring vacuum pumps have high energy consumption, low operating efficiency, long development cycle and high failure rate. In order to solve the above problems, based on FLUENT simulation software, this paper establishes a mathematical model for a kind of liquid ring vacuum pump that can realize radial clearance change by rotating the pump body, and carries out external characteristic tests to verify the accuracy of the simulation results. To investigate the influence mechanism of different radial clearances on the gas-liquid two-phase, pressure, velocity and inlet/outlet reflux characteristics of the internal flow field of the liquid ring pump, and to derive the influence law of radial clearance and vane wrapping angle on the suction volume, shaft power and efficiency by numerical calculation. The results show that by adjusting the radial clearance and vane wrap angle, the flow situation inside the pump can be effectively improved, and the suction efficiency and overall performance can be enhanced, which provides theoretical support for the research and development of the new liquid ring pump.