Abstract: At present, there isn't a quantitative analysis on acoustic emission propagation mechanism of RV (rotate vector) reducer. For this problem, this paper seeks to analyze and investigate the propagation mechanism of acoustic emission signals in RV reducer, and monitors and evaluates the reducer failures accurately, such as the reducer wear. Firstly, the propagation model of acoustic emission signal in RV reducer is built based on its kinematic mechanism. Then the wavelet transform analysis is used to obtain the time-frequency component features of acoustic emission signals at different frequency bands, and the trend evolution model of acoustic emission signals is derived. In the accelerated degradation tests of RV reducer, the evolution trends of acoustic emission signals in 4 different wear states are obtained, which proves the validity of the acoustic emission signal propagation model.