Abstract: In order to divide "three zones" of the depressing zones overlying a goal accurately, the guideline to divide the "three zones" is presented:specifying the height of the rock stratum whose stress surpasses the yield or shear strength of itself as the upper bound of the fracture zone, while specifying the height of the rock stratum whose two-way tensile stress both surpasses the tensile strength of itself as the low bound of the fracture zone. FLAC software was used to determine the boundary of a coal mine that was validated by the effect of corresponding methane drainage. The result indicates that the division guideline is rational and useful. This method can be used generally to divide "three zones" of the depressing zones overlying a goaf.