In order to study the effect of blade swept back on the cavitation flow field in tip region and performance of axial flow pump, the swept back 20° and swept back 40° impeller were redesigned based on the scaled model of TJ04-ZL-02 impeller in South to North Water Diversion Project. The whole flow field was calculated based on ANSYS CFX, the changes of pressure, cavitation and streamline distribution in the passage of prototype impeller and swept back impeller were compared and analyzed, and the effects of blade swept back on vortex intensity, vorticity and velocity field in tip region under different cavitation conditions were analyzed. The results showed that the NPSHa of the swept back impeller was decreased, and the cavitation area and cavitation volume fraction of the suction surface of the swept back blade were lower than those of the prototype blade. The backward sweep of the blade reduced the low pressure area of the suction surface and effectively inhibited the development of triangular cavitation cloud in tip region. As the blade swept backward reduced the pressure difference in the tip area, the tip leakage was decreased, and the vortex intensity and vorticity in the TLV core area were decreased with the increase of the swept angle. With the aggravation of cavitation, the vortex intensity and vorticity of TLV was increased, and the flow field in the tip area became more complex and disordered. Axial flow pump had the advantages of simple structure, large flow rate and high efficiency, and it played an important role in flood control and drainage, large-scale water transfer. The blade swept back improved the cavitation performance of the pump and had great potential in improving the cavitation performance of the axial flow pump.