Abstract: The flying gangue is a kind of special derivative disaster in the steeply dipping coal seam,which seriously endangers the safety of the working face equipment and personnel. It is essential to discuss the disaster mechanism to establish the protection system in longwall face along strike when mining the steeply dipping coal seam. Laboratory simulation was carried out on the basis of disaster measurement of flying gangue, the impact energy and energy recovery coefficient were used to characterize the flying gangue’ s hazard,impact energy were recorded and acquired by HDV and pressure sensors. The evolution characteristics of impact energy under different working conditions were analyzed by statistical principle. The risk discrimination model of flying gangue was established according to the curve of impact energy and energy recovery coefficient,and the damage level of flying gangue were divided. Then taking the energy of equipment ( personnel) as the control object,the energy absorption steep point and extreme point as the boundary,the flying gangue damage risk discrimination model was established to divide the damage level. The mecha- nism of flying gangue disaster was discussed on the basis of above discussion. The results show that the hazard of flying gangue by the impact energy and energy recovery coefficient reaches to the corresponding hazard level under the cou- pling of collision path and mode. The disaster process is the accumulation of impact energy in the state of free fall, splash,rolling and sliding,meets the movement,height,collision position and contact with the equipment. The impact energy can be converted into the elasticity of the device and the vibration damping between the components,resulting in the deformation of the component is greater than its ultimate deformation when the damage occurs. Lastly,the ration- ality of the energy recovery coefficient in the studies of theory and experiment were verified by simulation method.