A flow-field analysis model of the mixed-flow pump was established in order to study the flow field and pressure pulsation characteristics under different operating conditions. The unsteady numerical simulation of the whole flow field under different operating conditions was carried out by Large eddy simulation(LES)based on the CFX software. The results showed that the flow pattern was consis-tent at six channels except that a certain flow separation appeared on the suction surface near the guide vanes outlet at 1.00Qopt. When the rotating stall occurred, a lot of whirlpool developed near the suction surface of the guide vanes and the whirlpool scale increased first and then decreased from the inlet to the outlet at the guide vanes,more over the vortex core was attached to the suction surface where the pressure fluctuation was smallest. The pressure pulsationat different points was analyzed by FFT transform, which showed that the amplitude of the pressure pulsation increased graduallyfrom the hub to the rim. The distributiom of the pressure pulsation frequency at the outlet was similar to that at the inlet except that the amplitude decreased a little and the dominant frequency shifted to the low-frequency direction.Additionally, the pressure pulsation under different operating conditions was also analyzed. The changing regularity of three operating conditions was consistent.However, the frequency range is larger and the frequency components are more complex at 0.55Qoptcondition than at 0.75Qoptand 1.00Qopt condition. At 0.75 Qopt the low-frequency width is significantly reduced and the frequency of low-frequency pulsation was concentrated around 1N,white at 1.00Qopt,the frequency was not obvious except 6N and 12N, the amplitude of the pulsation frequency in the low-frequency range was significantly reduced, and the integral pulsation amplitude was significantly smaller than that under the other two operating conditions.
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