Abstract: In order to study the relation of the relevant factors on the drillhole pressure relief, by means of numerical simulation RFPA software, the paper analyzes the influence of different coal seam strength and different coal seam pressures and borehole diameters on the destroy radius of drillhole. Then by theory analysis and regression analysis, the paper draws the exponential function relation between the destroy radius of drilling hole and coal seam pressure in coal steam strength certain conditions, draws the inverse function relation between the destroy radius of drilling hole and the coal steam strength in coal seam pressure certain conditions, draws the logarithmic function relation between the destroy radius of drilling hole and the borehole diameter in coal steam strength certain conditions, draws the borehole destroying radius numerical expression among coal seam pressure,coal steam strength and the borehole diameter.