In order to reveal the effect mechanism of liquid viscosity on the gasliquid twophase distribution in a multiphase pump,the threestage oilgas multiphase pump was taken as the research object,and the oilgas twophase were selected as the transport medium.ANSYS Fluent was employed to simulate the twophase flow state and the twophase distributions under different viscosities were analyzed and summarized.The results show that the smaller the liquid viscosity,the greater the effect on the gas distribution in the pump;with the increase of the liquid viscosity,the gas pulsation along the streamwise in pump decreases;with the variation of the liquid viscosity,the distribution of the liquid in the pump is exactly opposite to the gas,and when the medium is heavy oil,the liquid aggregation phenomenon begins in 0.9 span at the impeller outlet in the pump;the increase of the liquid viscosity has a beneficial effect on the uniformity of the gas distribution in the oilgas multiphase pump.The research results can provide reference for the structure optimization and performance improvement of oilgas the multiphase pump.