Abstract: In order to grasp the characteristics of coal gangue interbed composite top coal caving in ultra-thick coal seam mining, and ensure the rationality of coal caving technology and high top coal recovery rate, this paper takes ultra-thick coal seam composite top coal mining as actual site conditions, analyzed the deformation, failure and strength characteristics of the composite coal and rock mass by using laboratory tests, numerical simulations, and on-site observations, and revealed the arching of the gangue-bearing coal body during the caving process, the gangue boundary and the caving law, and obtained the coal the distribution characteristics of gangue volume and weight. The results show that: the change of coal-rock proportion has obvious influence on the overall failure form of coal and rock, the damage of composite coal and rock mass is smaller than that of single medium, and the degree of development of coal mass fissures is higher, the greater the difference between the triaxial compressive strength and the uniaxial compressive strength of the composite coal rock mass, the greater the overall strength of the top coal body increases, the greater the probability of top coal arching, the larger the scale of the balance arch, and the orderly placement of single frames. The ratio of coal quantity to low-value area and high-value area of the release rate is about 1:3. The volume and weight of the composite coal rock mass are in accordance with the normal distribution, and the proportion of coal gangue blocks less than 40cm in length is 66%, but Its weight accounted for less than 15%. The main direction of the extra-thick coal seam containing gangue to increase the recovery rate of the top coal is to increase the discharge efficiency of blocks with a length of 40-100 cm.