Abstract: In order to study the influence of water on acoustic emission characteristics of coal,the unaxial compression AE (acoustic emission) tests under different moisture content coal are conducted.The results show that unaxial compressive strength of coal has no linear relation with the increase of the moisture content.Water weakens the stress concentration of coal in the inital process of loading,and it reduces the number and intensity of coal's internal failure in the whole process of loading. Moreover,the higher AE signal appears at the time of apparent stress drop. AE signal keeps in a low level before jumping,which reflects a process of energy accumulation.