Abstract: In order to solve the poor gas drainage effect of the through strata borehole in the outburst and hard seam of the deep underground mine, the through st rata deep borehole blasting was proposed and applied to the enhanced gas drainage method. With the numerical simulation and in combined with the theoretical analys is, the paper discussed the interface effect of the through strata blasting stress wave and explained the cracking evolution function mechanism of the through strata bla sting in the hard seam. The blasting stress wave would caused the reflection and transmission in the coal and rock complex medium with natural cracks, the compresse d wave and tensile wave would drive the crack expansion, the repeated roles would enhance the failure of the coal seam and the continued expansion of the cracks cou Id improve the permeability of the seam. A site application of the through strata deep borehole blasting was conducted in No.21 seam of Zhaogu No. 2 Mine. After the b lasting, the average gas drainage volume fractional of a single borehole was increased by 1. 04 ~ 2. 77 times and the average drained pure gas volume was increased by1.53~3.10times.