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In order to increase the range of high-efficiency zones in high specific speed mixed pumps, three types of hydrofoil schemes with maximum camber positions of 0.4, 0.5 and 0.6 were designed by using NACA four-digit airfoil camber lines superimposed with NACA66 thickness distribution. Based on the three hydrofoil schemes, the hydraulic performance of the mixed flow pump impeller with specific speed of 720 under multiple operating conditions was optimized. The research results indicated that after optimization, the weighted efficiency of the mixed flow pump impeller was increased by about 0.5 percentage points, expanding the operating range of the high efficiency zone of the mixed flow pump. The maximum efficiency of mixed pump impellers designed with different maximum camber positions of hydrofoils was not significantly different, the position of the maximum camber of the hydrofoil mainly affected the distribution range of the high-efficiency zone. As the position of the maximum camber moved backward, the high-efficiency zone range moved towards the vicinity of high flow and low head. Under the design flow condition, as the maximum camber position moved backward, the cavitation performance showed an improvement trend. When the maximum camber position was around 0.4 times and 0.6 times the chord length, it had a good inhibitory effect on the flow separation phenomenon near the inlet edge under low flow conditions and high flow conditions, respectively. When designing a mixed flow pump, the camber at the blade tip should be placed back and the blade root should be placed forward, which was beneficial for expanding the efficient range of the mixed flow pump. The research results can provide reference for the optimization design of fluid machinery under different operating requirements.