Abstract: It is difficult to accurately determine the height of caving zone in fully mechanized caving face in gassy mine, resulting in difficult maintenance at both ends in working face and difficult to determine the location of final hole of pre-pumping borehole. In order to solve this problem, according to the variation process of the pressure exerted on the coal seam floor in goaf of the roof breaking and caving, bending and subsidence after the mining of the working face, combined with the thickness and density of the overlying strata in goaf, a method to determine the height of caving zone development was proposed.Taking N1S2 fully mechanized caving face of Daping Mine as an example, the field test results show that the height of caving zone measured by the determination method is 88.65 m, the height of the caving zone measured by the drilling flushing fluid method is 88.20 m, with the absolute error of only 0.45 m.