To study the cavitation characteristics of a high-speed submersible axial-flow pump in high flow conditions, three cavitation models including Zwart, Kunz and Schnerr-Sauer were selected and the external and the interior characteristics of the pump were simulated in high flow conditions based on ANSYS CFX. The results show that the prediction accuracy of Schnerr-Sauer model is most consistent with the experimental value in high flow conditions. Compared with the other two cavitation models, the volume fraction of bubbles on the suction surface of the blade is higher, and the area with serious cavitation mainly appears near the leading edge and at the top of the blade for Schnerr-Sauer model. The cavitation of the blades becomes more serious with the increase of flow speed at the same cavitation number. The load increases first and then decreases from the leading edge to the trailing edge of the blade. The bubbles generate at the leading edge of the suction of the blade at first and then expend to the trailing edge of the blade along the mainstream flow direction until occupying the whole blade suction with the decreasing of cavitation number. The cavities in the trailing edge of the triangle cloud cavitation at the back of the blade are extremely unstable. As the impeller rotates, the bubbles at the trailing edge gradually shed and move toward the adjacent blades, resulting in erosion damage and load change of adjacent blades, affecting the hydraulic performance of the axial-flow pump.