Abstract: Based on DES vortex model and block structured grid technology,the adaptability and accuracy of DES model for the CAP1400 reactor coolant pump prototype and 0.4 scale model is verified through CFD numerical analysis and experimental investigation of exterior performances.Compared with the loading distribution on surface of the model pump rotor-stator cascade under different conditions,it is found that the blade load is very uneven,the blade load of impeller front cover is about 2 times than that of the rear; with the change of working condition,the difference of load guide blades is complex,and the load of the entrance section is relatively large under a large flow,even when changing the direction.Based on the turbulent vortex dynamics,the vortex motion and the evolution process of the rotor-stator cascade are clarified.The structure and evolution mechanism of the transient flow field of impeller and guide vane under the condition of noise disturbance are revealed.