Abstract: Based on the characteristics of the steeply dipping 1212(3) working face with the cataclastic regenerative roof of Panbei mine,the characteristics of secondary failure of surrounding rock and instability of support caused by coal seam mining have been discussed. The three-dimensional borehole imaging,similar simulation with acoustic emission and theoretical analysis have been used to study the structure and caving characteristics of roof and the support in stability model of fully mechanized mining face with steeply dipping seam. The consolidation and compaction state of cataclastic regenerative roof were described by the image of three boreholes. Then,similar simulation with acoustic emission and theoretical analysis method were used to explore the characteristics of the roof caving and sliding and the mechanism of support instability. The study shows that: ① affected by inclination angle,the characteristics of the compaction degree of cataclastic regenerated roof was that the lower part of the stope was higher than the middle part’s and the upper part of the stope with the weakest compaction degree. ② In the range of 3-5 m of cataclastic regenerated roof which was the key layer to change the position and state of support was easy to leak between the supports. ③The breaking of cataclastic regenerated roof had experienced six stages. Based on the strength of acoustic emission signal,the main causes of the fracture and instability of the cataclastic regenerated roof were the fracture of the upper cantilever beam and the slip of the cataclastic regenerated roof. ④ The upper part of stope was marked as the key prevention and control area of support stability,based on the field support load data which had verified the accuracy of similar physical simulation. ⑤ Based on the comprehensive analysis of the relationship between cataclastic regenerated roof and the support,the dumping and sliding instability models of steeply dipping stope under the cataclastic regenerated roof was constructed. The force characteristics of the support were analyzed and the inter-forces of the support under the critical state of tipping and sliding were -126. 8 kN and 86. 2 kN,respectively,which revealed that the position of cataclastic regenerated roof load had a significant influence on the stability of the support. ⑤ The trinity coordinated support system was discussed which included the protection of coal wall,the control of roof and the stability of support.