Aiming at the problems of poor roof stability and serious asymmetric failure of surrounding rock in the withdrawal entry with large mining height, taking the withdrawal entry of 2101 large mining height face as the research object, the stability of roof broken structure in the withdrawal entry is systematically studied by theoretical analysis, numerical simulation, mechanical modeling and other research methods. The key factors affecting the fracture characteristics of the basic roof are expounded. The failure characteristics of surrounding rock of roadway under different broken structures are analyzed. The structural mechanics model of "long key block" is established, and the formula of critical resistance of support is deduced. The calculation results show that the resistance affluence coefficient of support in 2101 mining face is small, and support management needs to be strengthened. The research results will provide theoretical guidance for the large-scale mining equipment safe and fast moving.