Multiphase pump is a new type of pressurizing equipment which combines the performance of the axial flow pump and compressor.The dynamic and stator interference between the impeller and diffuser will reduce the stability of the pump and cause vibration.In light of this issue,based on the SST κ-ω turbulence model,the ANSYS CFX software was used to carry out the steady numerical simulation of the pump under different axial clearances when the inlet gas void fraction was 8%.And the effect of the axial clearance on the internal flow and the pressure load of the diffuser blade of the pump under the design condition were analyzed.The research results show that under the design condition,the increase of the axial clearance can make the gas phase distribution uniform and reduce the area with large turbulent kinetic energy in the diffuser,while the axial clearance has little effect on the distribution of the gas phase and turbulent kinetic energy in the impeller.Additionally,in the diffuser inlet,the pressure of the blade suction side decreases with the increase of the axial clearance,and the pressure change of the suction side with the axial clearance is more dramatic than that without the axial clearance along the streamline.At the same time,the axial clearance has little effect on the pressure variation of the pressure side,which gradually decreases from the hub to the shroud of the diffuser.The research results can provide reference for improving the hydraulic performance of the multiphase pump.