To further investigate the gasliquid twophase flow characteristics and vortex mechanism in the low specific speed centrifugal pump,the ANSYS CFX software was used to simulate the flow characteristics under different inlet gas void fractions.The gas distribution and vortex location were analyzed.The effect of the gas on the flow state in the pump was summarized.The results show that with the increase of the inlet gas void fraction,the pressure gradient in the impeller becomes larger,and the high pressure region at the volute outlet increases,the low pressure region at the impeller inlet gradually disappears;when the inlet gas void fraction is equal to 10%,there is a relatively obvious gasliquid concentration at the impeller inlet.It has also been found that gas phase concentration occurs mainly at the blade pressure side,the gas phase concentration corresponds to the vortex,and with the increase of inlet gas void fraction,the work capacity of the pump becomes worse.The research results provide reference for hydraulic design and structural optimization of centrifugal pumps.