Pressure fluctuations inside centrifugal pump, especially those near the volute tongue, are the primary excitations to pump vibration and noise. The performance and pressure fluctuations of a centrifugal pump running at different flow rates and variable speeds were experimentally studied. The pump performance measurement showed that the pump worked at low flow rate condition, and the pump hydraulic performance varied with the rotational speed according to one-dimensional design theory. The pressure fluctuation measurement showed that discrete components were the main contributions in the pressure fluctuation spectra, especially the blade passing frequency (BPF) and its second harmonic. The overall strength of pressure fluctuation was approximately 1% of the reference dynamic pressure, and it varied in a quadratic function form with rotary speed. At a constant rotation speed, the pressure fluctuation magnitude at the outlet side of volute tongue had no obvious change with the decrease of flow rate, but places at the inner side and tongue tip experienced noticeable increase at sufficiently low flow rates owing to the pressure fluctuations below BPF. The study provided a basis for future study of flow-induced pump vibration and noise.