Abstract: In order to obtain the causes on the crushed accident of the hydraulic support in the coal mining face of Ganhe Mine, a roof dynamic monitoring and mea suring system was applied to timely monitor and measure the working resistance of the hydraulic support. In accordance with a mine strata pressure theory, the variatio n conditions of the initial support force of the powered support, the terminal resistance of the circulation and the open rate of safety valve before and after the powered support crushed and the stressed condition of the shield beam was analyzed with the basic principle of the engineering mechanics. The analysis showed that the main C auses of the powered support crushed accident were a slow pushing forward speed of the coal mining face and the powered support long timely in a high loading statu s. The difference of the safety valve set values between the powered supports was high. A high roof subsidence value caused a cutting height obviously reduced and th e shearing force of the powered support shield beam obvious increased. The crack water of the sandstone in the overburden strata above the coal mining face would m ake a frictional cofficient reduced between the roof strata above the coal mining face and would intensify the mine strata pressure behavior degree of the coal mining f ace. According to the above causes, an optimized powered support design was provided, a hydrogeological and mine strata pressure observation of the coal mining fac e was intensified, a roof control of the coal mining face, the face pushing forward speed increased and other measures were enhanced.