In the Yangliu Mine in Huaibei Coalfield, violent magma intrusion produced two layers of the igneous cover sills and the annular dike and caused the ejection of gas and water in the bed splitting from the surface well that destroyed the gas extraction system on the surface. The source, flow characteristics and hazard of the gas in bed splitting under igneous sills were researched via laboratory experiments, theoretical analyses and numerical simulations. The experimental results indicate that the shorter the distance from the igneous sill and the larger the thickness of the igneous sill, the greater will be the amount of the thermal evolution, the pyrolysis stoma, the coal adsorption and desorption ability and the risk of outburst, six coal samples collected at different distances from the igneous sill. The first breaking length of the igneous sill, the volume of the bed splitting, the gas pressure and flow rate in the bed splitting and the accumulative volume of the gas ejected from the surface well #2 were theoretically calculated. The laws of the bed splitting development under the igneous sills were simulated, consistent with the theoretical calculation results. The regional control and prevention technologies for coal seam gas under igneous sills were proposed and applied. Then the safety of the first-mining seam production and the gas extraction in the adjacent seam and bed splitting via the surface well was ensured, and no accidental gas and water ejection occurred.