Abstract: In order to study acoustic emission characteristics of coal samples with different strength under uniaxial compression, experimental study of hard coal, medium hard coal and soft coal was carried out by using RMT-150C rock mechanic test system and CDAE-1 acoustic emission instrument. In order to solve the problems of different interference noise and signal processing in the acoustic emission test, decomposition, de-noising and reconstruction for the acoustic emission signals were conducted through wavelet packet transform. The results show that the processed acoustic emission signals can more clearly reflect the variation characteristics of buckling failure under uniaxial compression. Soft coal, medium hard coal and hard coal have different acoustic emission characteristics. With the increase of coal strength, acumulative energy and acumulative counts of acoustic emission decrease gradually at the instability failure, energy and count peak of acoustic emission of coal samples also decrease under stress, and the released energy at the peak decreases too.