Based on the Navier-Stokes equation set and the standard k-ε turbulence model, the numerical simulation of the flow field in axial flow pump was conducted on the platform of commercial software CFX by using SIMPLEC method. The pump performance curves resulted from numerical simulation was verified with the experimental results; and then, the computational distribution of relative velocity and streamline in 90% blade span and the discharge region was compared with the results measured by PIV in the same positions, and they were in a good agreement, which indicated the validity and correctness of the numerical simulation. Furthermore, the flow features and the reasons caused efficiency fall of axial flow pump under different flow rates were analyzed, and the results provided some references to the internal flow analysis and the performance improvement of axial flow pump.