After the coal seam is extracted, the original rock stress is released, under the longwall mining full caving conditions, in the overlying strata above a goaf, a caving zone, a fracture zone (or water suture zone) and a bending belt will be formed, as is normally called the "three zones". In order to calculate two zones' (break and crack zones) height in the overlying strata of the underground coal mining more accurately, with consideration of the fact that the two zones' calculation formula in the specifications covers a too broad range, by using Matlab for the curve fitting, this paper proposes calculation formulas based on the overlying strata strength and the mining thickness, and with a functional relationship between them. The accuracy of the calculation is improved. Through the calculation of the two zones' height of the overlying strata of 22101 working face in Huoluowan coal mine, the calculation method of this paper is verified. It is indeed a more accurate calculation formula for the zones' height for the single long wall fully caving coal.