Abstract: To parameterize the velocity moment distribution, Parameter a0, relative coefficient of the distribution curve of the dimensionless velocity moment along the streamline, and parameter P, curve derivative value in the position of blade trailing edge, were selected to be velocity moment distribution parameters by theoretical analysis. Based on the design platform of iterative calculation of direct and inverse problems of the mixed-flow pump impeller, a series of mixed-flow pump impellers were designed with different combinations of velocity moment distribution parameter values. By solving N-S equation and RNG k-ε turbulent model equation, the three-dimensional turbulent flow field inside the mixed-flow pump impeller was simulated on the basis of SIMPLEC algorithm. Thus, the relative pressure and the relative velocity distributions were determined and the hydraulic efficiency was estimated. The results show that, velocity moment distribution parameters have direct influences on the blade wrap angle and the trailing edge, which has further effects on the internal relative velocity distribution, the internal relative pressure distribution and flow stability. Reasonable selection of velocity moment parameters can strengthen the control of blade over fluid motion, improve internal pressure distribution of impeller and realize better hydraulic characteristics of the impeller. In addition, the parameterization method of the velocity moment distribution developed in this paper can also be beneficial to setting the velocity moment distribution though the procedure of impeller design of the mixed-flow pump.