A method of agglomeration detection in horizontal stirred bed reactors was obtained based on the frequency of acoustic emission (AE) signals vary with different sizes of particles stricken on the wall. The AE signal was dealt with by the method of spectrum analysis and wavelet analysis. It was found that the low frequency band energy ratio of AE signals (d6~d7) increased as the agglomerations were added in the reactor. So this method could predict the agglomeration environmental friendly with fairly good accuracy.