Abstract: Due to the particularity, fully mechanized coal face with large mining height or extra large mining height, the roof structure movement form is different compared with secondary mining height working face. After the mining influence, through the study of movement laws of overlying critical layer, the results show that overlying critical layer is usually in the form of “cantilever beam” breakage structure under the condition of large mining height or extra large mining height, also forms stable hinged structure sometimes; the upper critical layer usually can form “masonry beam” structure; when the upper key strata occurs fracture, the lower key layer will also be affected by the fracture of upper key layer; strata behavior and periodic weighting interval of working face does not directly affected by the breakage of upper key strata but by whether the key layer is breakage or not.