Abstract: In order to study the effect of crack evolution on gas permeability of coal during bearing process, mechanical, acoustic emission and permeability tests are carried out on two types of coal samples.The main conclusions are as follows:before the peak, the change trends of strain, acoustic emission ring number and permeability of coal samples are consistent.The coal strain increment experiences three stages:deceleration, homogenization and acceleration, while the change trend of acoustic emission ring number and permeability experiences three stages:decrease, stability and increase; after peak, there are great differences between anthracite and bituminous coal.The strain curves of the two anthracite with higher strength dropped steeply, and there are no multiple residual strength values, and the acoustic emission ringing number data and permeability data could not be measured after the peak.The strain curves of the two bituminous coal with lower strength decreases slightly, with multiple residual strength values, and the number of acoustic emission rings and permeability can also be monitored; the maximum permeability are all bigger than the initial permeability.The maximum permeability of two anthracite coal is at the end of the curve; the maximum permeability of the two bituminous coal is coincident with the strength value point, increasing the initial permeability.The evolution of coal crack plays a key role in controlling the change of permeability, and crack development of medium hard coal contributes to increasing gas permeability.