Abstract: In order to study the rotor-stator interaction in the wake region of the axial-flow impeller, the axial-flow pump model for South-to-North Water Diversion Project model was simulated based RNG k-ε turbulence model and the SIMPLE algorithm. The calculated values by steady simulation were compared with the experimental results to verify the computational grid and the applicability of turbulence model, and the unsteady field was simulated based on the steady results. The numerical results show that the relative error of Head is 4.56% and efficiency is 2.78% in optimal condition compared with the experimental data. In small flow rata condition, three peaks and three second peaks occur on the meridional velocity at axial flow impeller outlet in the circumferential direction. As the flow rate increases, the number of the velocity peak at impeller outlet is same to the guide-vane blade number. In the small flow rate and design conditions, the single-cycle time-domain of the pressure fluctuation in the impeller wake region appears three peaks and the additional three secondary peaks when flow rate increases. The main frequency of pressure fluctuation in different flow conditions is mainly blade frequency, and the other harmonic frequencies are the times of the fundamental blade frequency. The amplitude of pressure fluctuation frequency increases rapidly as the flow rate decreases.