Based on CFD software platform, the joint surface between the rotor and stator of the hydraulic retarder was defined as interface to transfer the flow data of different subdomains by moving mesh theory. Numerical simulation of different dip angle of hydraulic retarder was performed with the RNG kε turbulence model and SIMPLEC algorithm simultaneously. The characteristics of velocity and pressure distribution were analyzed through the numerical simulation and postprocessing. By the calculation braking torque and the simulation result, the brake increases with the blade dip angle decreasing, but the brake torque decreases when the dip angle is smaller than the angle of 43 degree.