Abstract: With the cavitation visualization experiment rig involving Venturi pipe segment, the instantaneous cavity profiles were captured using high-speed camera, and the pressure fluctuations in the flow field were recorded using high-frequency pressure fluctuation measurement system. Pure water and NaOH solutions with mass fractions of 0.5% and 1.0% were selected as liquid mediums. The effect of volumetric flow rate of the liquid medium on the cavitation was investigated. The comprehensive analyses of cavity morphology, power spectra density and root mean square（RMS） energy of pressure fluctuation were implemented. The results show that the cavitation intensities in the two NaOH solutions are relatively higher than that in pure water, and the increasing of NaOH mass fraction can promote the severity of cavitation. In pure water, backflow of cavitation bubbles at the downstream end of cavity zone is remarkable. The cavitation can stimulate high-frequency fluctuations in the NaOH solutions, while the power spectra density is not positively related to the cavitation intensity. The position of the maximum RMS energy of pressure fluctuation shifts downstream with the increasing of flow rate, and the highest RMS energy of pressure fluctuation is obtained in 1.0%NaOH solution.