Aiming at the leakage problem of axial tip clearance of the liquid ring pump impeller, dielectric barrier discharge plasma excitation was proposed to control the gas phase leakage flow in the axial clearance of the liquid ring pump. The interference of plasma on leakage flow field under different excitation voltages was simulated by coupling phenomenological model, RNG k-εturbulence model and VOF gas-liquid two-phase model. The control mechanism of plasma excitation on clearance leakage flow field was investigated. The results show that the direction of the wall jet induced by plasma excitation was opposite to that of the clearance leakage flow. The reverse wall jet can effectively suppress the leakage flow intensity, improve the secondary flow caused by the clearance leakage flow to a certain extent, and reduce the clearance leakage flow loss. Meanwhile, the vortex structure was induced by plasma excitation in the non-clearance near-wall region, which caused additional hydraulic loss. The excitation voltage and position had an important influence on the control effect of leakage flow. The plasma flows control effect of 15kV excitation voltage was significantly better than that of 10kV excitation voltage. When the excitation position was near the outlet of blade tip clearance, the plasma excitation had a good suppression effect on the leakage flow. The research results can provide a theoretical reference for the performance optimization of liquid ring pumps.