The cavitation characteristics were analyzed in this paper for the flood relief mid-outlets of Baise Multipurpose dam project, on the basis of depressurized model test of 1:50 in a specially designed vacuum chamber. The results of test demonstrate that there exists relatively distinct cavitation cloud at the gate slots and outlet diffusion zones of spillways. Mutual disturbance of cavitation noise from two sources leads to the relationship curve becoming concave downward and the frequency spectrum sound pressure level decreasing correspondingly when h is close to hm (h/hm = 1). Its pattern is not in conformity with the general law. The discovery may have certain supplementation for the standard of judging the cavitation emergence
