Abstract: Abstract:According to the charcaters of overlying strata structure and failure in fully mechanized working face of extremely thick coal seam,and the disaster of pressure frame in CuiMu,the author analyzed the controllable and uncontrollable factors of crushing,proposed effective prevention techniques on the principle of optimizing the controllable factors and regulating uncoontrollable factors. The studies have shown that the factors cluding support resistance,setting load,support efficiency,roof water and the speed of working are particularly critical to the crushing preventionm,by increasing support resistance and setting load, optimizing support construction, accelerate the speed of face advance, weakening the impact of roof water can effectively prevent the occurrence of large crushing disaster incidents in extremely thick seam mining face .

Key words: Key Words:extremely thick coal seam, fully mechanized working face, crushing mechanism, prevention and control technology