Abstract: According to 6206^# fully mechanized caving face mining conditions in Lu'an Mining Area，on the basis of analyzing roof overburden combination and the mechanical structural characteristics, the development characteristics of the fractured zone in the medium hard overlying strata under full-seam mining conditions are studied by field observation and numerical and physical simulation. Through combining with the exsiting field observation data and regression analysis, it can be seen that the development height of the fractured zone in the medium hard overlying strata is directly proportional to the total mining thickness. In comparison with the empirical formula, the method can better reveal dramatic failure of overlying strata under such a mining condition.