To study the cavitation effect of an axial flow pump on its internal flow characteristics and energy conversion, constant cavitation calculation was performed using the SST k-ω turbulence model and the homogenous multiphase flow model for an axial pump. The results show that the cavitation volume fraction of the axial pump gradually increases as the effective net positive suction head a decreases, which can induce undesirable flow states like jet-flow or vortex on the surface of the pump blade and can lead to an adverse impact on the homogeneity of the outlet flow field. From the pump blade inlet to the outlet, the relative velocity of the liquid in the cavitation region is higher than that before cavitation while the absolute velocity and the static pressure are lower than those before cavitation. In the axial direction, under the operation condition of no cavitation and the early-stage of cavitation, the static and dynamic lift remain constant. As the inlet pressure of the pump gradually decreases, the static lift doesn’t change but the dynamic lift rises slightly, which results in a small increase in the hydraulic performance of the pump for a=5. 33 m. For a= 4. 71 m, the static lift decreases with a drop range larger than that of the dynamic lift rise, resulting in a significant decline in lift efficiency. As the cavitation degree increases, the static and dynamic lift continue to decline, and the hydraulic performance of the axial pump drops sharply.