Abstract: Based on dual media model structure of pore and fracture in coal seam, the dynamic and changeable models were established for pore permeability rate and fracture permeability rate of coal seam due to the difficulty of gas extraction caused by tough gas resolving and low permeability rate in coal seam with water inside. Besides, the coupled equations of gas-liquid-solid multiphase were developed for gas extraction in that of coal seam and the gas extraction effect was researched through numerical simulation under the impact of horizontal stress, coal solidity and water. The results of study show that the larger horizontal stress decreases the gas extraction volume through compressing the fractures of coal and the more water remained in coal decreases the gas extraction volume as well. The models could be applied to the influence factors analysis during gas extraction as well as the prediction and estimation of gas extraction volume in coal seam.