Abstract: Considering the special geological conditions of fully mechanized caving face in Baode Coal Mine，the basic roof stability of coal face has been analyzed by using "S-R" stability theory of voussoir beam mechanical model. Then this study obtained the reasons of pressing frame accidents in coal face and provided relative countermeasures. The direct reason caused roof collapse is the increased deformation of basic roof rotation, and the support load occurs stress concentration. Fundamental reason is that scour structure leads to thinness of immediate roof.