Abstract: The characteristics of pressure fluctuation in a submerged circulative impinging stream reactor (SCISR) were experimentally studied.The instantaneous signals of pressure fluctuation resulting from the turbulence in the SCISR were measured by sensors and recorded by a computer.The pressure signals at some special positions were sampled at different rotary speeds of propeller.After analyzing the signals with the Power Spectrum method，it was found that there was an inherent frequency in the dynamic pressure signals.The inherent frequencies of the point on the impinging plane were greater than 1000 Hz，so the pressure fluctuation was called high-frequency fluctuation.The fluctuation velocities with high inherent frequency resulted in a strong shear force field，which enabled the fluid to mix quickly on the micro-scale and the agglomerates of solid particles to disperse effectively.