Abstract: Coal wall instability failure characteristics were analyzed in view of large mining height, and the existence of coal wall weaken points (weaken surface) leading to root causes of large mining height local instability is proposed. According to characteristics of coal wall buckling instability region, coal wall instability sliding mechanics model was established by using Bishop's slice method, and calculation formula of coal wall stability was deduced. In combination with large mining height actual engineering geological conditions in Zhaogu No.2 Coal Mine, it obtained coal wall weaken points (weakened surface) of large mining height working face in different locations of the critical instability of slip plane, and then instability and failure of coal wall coal area was predicted. Measures of preventing damage coal wall instability were proposed on the basis of this, and instability and failure of large mining height coal wall brings to production of safe hidden trouble was effectively solved.