Cavitation performance curves of the model axial-flow pump were established on the basis of the hydraulic characteristic test with a numerical simulation of steady cavitating flow. Under the designed working conditions, the whole flow passage of the model axial-flow pump was carried out using a full cavitation model and a mixed two-phase flow model. The cavitation flow of the impeller was analyzed by comparing the primary cavitation, critical cavitation, and serious cavitation. The distribution of static pressure and vapor volume fraction of the blade’s suction surface were observed and the vapor volume fraction of the axial section was obtained. The simulation results showed that cavitation first occurred on the local low-pressure area on the back of the blade’s leading edge, which was close to the tip. When the pump ran at its critical cavitation point, the chord length of the cavitation region was 2/3 of the length from the back of blade’s leading edge to its trailing edge, approximately 50% of the back of the blade. After further increasing cavitation, the cavitation region extended towards the trailing edge and the fraction of its volume became larger. When local cavitation occurred in the impeller, it did not affect the power of the pump; however, when cavitation was serious, the over-current cross section close to the leading edge was obstructed, and the pump’s power declined seriously. The results of the simulation agreed with basis of the hydraulic characteristic test, revealed the axial flow impeller cavitation within the static characteristics. 