In order to solve the problem that the grouting material is not dense at the bending position of the prestressed bending bellows, a method for monitoring the compactness of the prestressed bellows based on the piezoelectric wave method is proposed in this paper. A piezoelectric ceramic piece is pasted at each top and bottom of the four crosssections of the prestressed bellows. Through the longitudinal monitoring mode of “regional crossing” with single transmitting and single receiving, the variation laws of the amplitude, frequency and wavelet packet energy of the received signal under nine grouting working conditions are analyzed. When the grouting material in the bending bellows is dense, the power spectrum density and the wavelet packet energy changed more obviously, which verifies the effectiveness of the piezoelectric wave method.