Abstract:It is very important to determine the key strata and its fracture of roof rocks to control. Taking Baijiao mine as an example,it is used three methods which are analog simulation experiment,key strata theory and numerical simulation to calculate the key strata and its fracture of hard and soft composite roofs. The results show that the first hard strata to the third hard strata break one after another,which are inferior strata in the roof. The fourth hard strata to the sixth hard strata are the combined key strata;and the average interval of roofing breaking is 114 m. Breakage of the key strata over this working face leads to strata behavior when it is progressed at 108.2 m. Meanwhile,it can determine the key strata and interval of roofing breaking of hard and soft combined roofs accurately with the three methods;and it can provide references to working face support and ground pressure control.