Abstract: For rock burst disasters in deep high gassy coal seam, we discuss occurrence mechanism of gassy seam rock burst from the influence of gas on coal body strength, the crack phenomenon of gas coal in unloading condition and gas and coal accumulation static energy. Through theoretical deduction, firstly gas reduces the strength of coal and reduces the energy that coal destruction required; besides, coal seam containing gas suddenly unloaded, spall fracture is caused by the joint action of ground stress and gas, which weakens ability of resisting deformation of coal; under the combined action of concentrated dynamic load and static energy, the energy criterion of rock burst in gassy seam is established. It is pointed out that coal containing gas is more prone to the rock burst. Besides, it often appears the phenomenon of abnormal gas outburst after the rock burst; gas accumulation brings hidden trouble to safety production, even, causes coal and gas outburst and other dynamic disasters.