Variable eccentric radial piston pump is a new and highly energy efficient one, which has been widely used in the hydraulic transmission system with high pressure and large flow rate. A brief introduction was given on a new variable eccentric radial piston pump’s mechanical structure and operation theory, which has 11 plungers, at the flow of 500 mL/r and the pressure of 35 MPa. The three-dimensional (3-D) models of the pump were built with the aid of the 3-D modeling software Pro/E. The dynamic characteristics of internal flow fields of speed and pressure of the pump were analyzed when operated stably with using of the software of Fluent-3D, by which the charts of pressure of the internal flow field and the speed distribution of the pump were obtained. According as the simulation results, the structure of the pressure relief groove is improved. The analysis of finite element analysis (FEA) results of the improved show that phenomena of pressure impact of the pump is significantly improved.