Abstract: The numerical simulation is based on N-S equations and the standard equations κ-ε turbulent model. By using SIMPLE algorithm and Mixture model, a pump inversion whose specific speed is 41 is useed as the object of the study. By using CFD method to conduct numerical simulation of PAT modes in air content of 0%, 5%, 10% and 15%. The external characteristics, static pressure and the radial force of the size and direction of PAT are obtained in different volume fractions of gas. The influence of radial force on PAT is attained and the result shows that numerical simulation has certain guiding significance for the design of PAT.The results indicate that the pressure head of PAT increases with the flow increased.The radial force of PAT increases rapidly as the flow increases and decreases rapidly as the air content increases. The direction of the radial force is concentrated in the Angle between 80° to 130°.