Abstract: In order to study the influence of immediate roof thickness on thick-hard roof mining, taking engineering specifications at 11313 longwall working face in Pan'er Coal Mine as research background, based on analyzing physical and mechanical parameters of coal and rock, the UDEC^2D model was built to simulate patterns of ground pressure with fully mechanized coal mining in different thickness of immediate roof including 0 m, 1.58 m, 5 m and 9 m. Results show that immediate roof is the key role in transferring load between thick-hard rock and hydraulic support set at working face. When the thickness of immediate roof is thin of 0 to 1.58 m, the first weighting interval of main roof is less than the condition of 5 m to 9 m. under the condition of thin immediate roof, the dynamic load coefficient of support is larger, and wall caving of working face is serious. However, when the thickness of immediate roof is from 5 m to 9 m, weighting time and interval will be increased and working resistance of support will be needed.