In order to explore the acoustic emission characteristics and damage evolution mechanism of granite in brittle and ductile failure processes, we carry out uniaxial experiment on granite, and simulated experiment under different confining pressures through PFC(particle flow code). On the basis of test, we obtain the acoustic emission curve in failure process and reproduce the evolution process of internal damage. Test results are as follows: 1) critical confining pressure from brittle failure to ductile failure is 100MPa; 2) lag effect of maximum acoustic emission intensity is significantly affected by confining pressure in brittle failure, and the greater confining pressure is, the less obvious lag effect is; 3) in ductile failure, maximum acoustic emission intensity and peak stress appear in the same time without lag effect; 4)acoustic emission curve has single peak in brittle failure ,while gentle curve form in ductile failure; 5)there are few internal serious damage zones in brittle failure with concentrated distribution, and crack extension tends to be in the same direction; 6) internal serious damage zones which distribute throughout the specimen in ductile failure are more than those in brittle failure, and crack extends mainly along two mutually orthogonal directions ;7) rupture angle gradually reduces as confining pressure increases, and rupture surface transforms into crushing zone with the increasing of confining pressure; 8) in brittle failure with low confining pressure, rock is cut into a few blocks ,while in ductile failure with high confining pressure, the rock destruction is comminuted.