Abstract: The characteristics of pressure fluctuation between the rotor and stator in the model pump of canned nuclear coolant pump were researched. The time domain and frequency domain of pressure fluctuation were obtained with CFD method and a detached eddy simulation (DES) method. The results show that the pressure fluctuation between the rotor and stator is dominated by the blade passing frequency, and it is due to the jet wake of the impeller’s trailing edges periodically cutting the guide vane’s leading edges. The amplitude of the pressure fluctuation of the outlet position reaches the maximum, and the amplitude of the pressure fluctuation decreases along the counterclockwise direction. The amplitude of the pressure fluctuation is small under low flow rate, and the volatility of pressure fluctuation is larger with the flow rate becomes larger. There are some low pressure regions between the rotor and stator, and the low pressure region propagates at the impeller rotational speed.