Abstract: For the problem that the gas drilling extraction radius of coal seam with large moisture content are greatly influenced by the moisture content, in this paper, by means of the dynamic relationship between moisture content and permeability of coal, combining with comparative analysis of the error and gas pressure value parameter fitting, the Klinkenberg effect equation which is suitable for water-gas-coal three phase coupling and the relationship equation between porosity and moisture content of coal body are obtained. Based on the above model, combined with the actual conditions, the best extraction radius of layer-through drilling is simulated; in the field application, the percent of gas extraction is about 73.2% when borehole spacing is 10 m, and the extraction effect is good.