Abstract: A number of coal and gas outburst had occurred in Qianling Coal Mine, due to its complicated geological structure and serious magma erosion. In order to provide an effective guide for gas control under the special geological condition, based on the geological structure of the coal mine and the erosion condition of magmatic rocks, it used the approach of laboratory test and site survey test, chose the representative measuring points, studied the coal seam gas occurrence law in magmatic rocks erosion area under complicated geological conditions. The results showed that under the effect of the overlying magmatic rocks pyrolysis and metamorphic superimposed, the metamorphic degree of coal seam got higher, regional gas outburst judging indexes increased. High temperature pyrolysis of magma caused the coal seam secondary hydrocarbon generation, the overlying magmatic rock bed and the low permeability rock in synclinal axis both played a good enclosing effect on the gas accumulation, thus caused the gas pressure and gas emission increasing in synclinal axis, increased the risk of coal seam gas outburst.