Abstract: In order to study the influence of the matching of guide vane and impeller to the performance of nuclear reactor coolant pump and the radial force distribution of impeller, the unsteady numerical simulation was done for nuclear reactor coolant pump under different schemes by using CFD technology and the experimental verification was done. The results show that the calculated curves and experimental curves of the head and efficiency for nuclear reactor coolant pump are consistent. The relative error of efficiency is about 2.5% and that of pump head is about 4%. The numbers of impeller blade and guide vane blade have a significant impact on pump performance and can effectively improve pump performance by appropriate matching. Due to different matches of guide vane and impeller, the radial force distribution of impeller has big difference, and the cyclical fluctuation and pulsation frequency of radial force mainly rely on frequency which the impeller blades cross the guide vane blades. The pulsation amplitude of the radial force increases and the rate of change reduces with the decrease of flow in low flow. The pulsation amplitude of the radial force increases with the flow in high flow.