Abstract: In order to study the internal and external failure modes and crack evolution law of mine filling, Use PCI-2 acoustic emission tester and pressure testing machine to analyze the strength, AE activity and crack evolution of gangue backfill under different water cement ratio and cementitious materials.the results showed：(1)The minimum 3-day strength of gangue filling body is 3.6 mpa, which meets the filling requirements. The time of maximum stress value can be delayed by appropriately increasing the water cement ratio.(2)When the stress is the largest, AE activity is the most intense, and the cracks of the specimen are connected up and down, showing tensile failure.(3)The crack evolution of gangue specimen is divided into closed compaction stage, linear elastic deformation stage, unstable propagation stage and post-peak deformation stage. During the closed compaction stage and linear elastic deformation stage, the AE signal of the specimen was weak ; The AE signal of gangue specimen in unstable stage is violent and the internal particle collision is obvious. The deformation after the peak is large, and the AE activity decreases sharply.