Abstract: The sonochemical yield of 815kHz ul rasound in a reverberation field of small scale was investigated with fluorescence spectrophotometer. It has been shown that the sonochemical effect in a reverberation field is of two characters: 1, Cavitation threshold sound intensity decreases and apears to be 0.3W/cm² (while it is aboul 0.7 W/cm² in progressive field); 2, Sonochemical yield increases with rise of sound intensity following the threshold at first, and then it suddenly increases (while it tends to a saturation value in field of prograssive wave). Theoretical analysis performed in this paper shows that the decrease of threshold is caused by increase of sound energy density in the reverberation field, and the steep point in the curve of sonochemical yield as sound intensity resullts from the liquid surface disturbance of the sound radiation pressure. This paper therfore, has experimentally and theoretically shown that in order to get easily and more sonochemical yield a reverberation sound field in teactor must be established.