Abstract: To explore the mechanism of hydraulic support pressure and the calculation method of working resistance for super-high mining height fully mechanized top-coal caving face in extra-thick coal seam, taking the Tashan mine field in Datong mining area as the background, through similar simulation experiments and theoretical analysis, the structural characteristics and evolution laws of the overlying rock strata on the super-high mining height fully mechanized top-coal caving face in extra-thick coal seam were studied. The structural models of “composite simply supported beams” and “masonry beams” of the overlying rock strata were established and their mechanical analysis was conducted. The research results show that: The fully mechanized top-coal caving face in extra-thick coal seam has a large mining space and a wide range of affected overlying rock strata. When there are multiple thick and hard rock layers in the overlying rock strata, a masonry beam structure is easily formed at high positions, and a “composite cantilever beam” structure is formed at low positions. As the working face advances, this structure undergoes a motion process of “rotation-separation-reverse rotation-sliding”. After the combined cantilever beam breaks, it rotates towards the side of the goaf and exerts deformation pressure on the hydraulic support. Subsequently, the “combined cantilever beam” structure slides and separates, forming a “combined simple beam” structure, and transfers the load of the overlying rock strata to the hydraulic support at the working face through the top coal. When the load exceeds the working resistance of the support, it is prone to cause a support collapse accident. Through mechanical analysis, the expression of the lateral support force of the coal wall at any layer of the “combined simply supported beam” structure was obtained, and the pressure acting on the top coal above the support was iteratively obtained. A calculation method for the working resistance of hydraulic supports in a super-thick coal seam with a large mining height under the action of a low-position “combined simply supported beam” structure was proposed.The load of the “composite simply supported beam” structure acting on the hydraulic support is determined by the thickness, length, breaking angle, and rotation angle of each rock beam in the structure.The above research results provide a theoretical basis for further analyzing the relationship between the support and surrounding rock in the super-high mining face of ultra-thick coal seam with fully mechanized top-coal caving mining, which is the core issue of mining pressure control. It also has certain reference significance for the selection and automatic control of intelligent ultra-high mining equipment in ultra-thick coal seam.