219%、105%和205%。The pressure fluctuation of turbulent flow, especially near the volute tongue in a double-suction centrifugal pump, is the primary reason of pump vibration and noise. This unsteady flow feature was investigated by large eddy simulation (LES) method with sliding mesh technology. The results showed that the blade passing frequency dominated the pressure fluctuations near the volute tongue at the design and large flow rate condition. At the small flow rate condition, the frequency which was lower than the blade passing frequency became dominative in the pressure fluctuations. The amplitude of the pressure fluctuation became higher when the flow rate was farer from the design flow rate. At the 62%, 80% and 120% of design flow rate conditions, the pressure fluctuation amplitudes were respectively 219%, 105% and 205% larger than the amplitude at design flow rate.