Abstract: Due to the widespread intrusion of diabase in roof of Ⅲ₃ coal seam in Xuandong No.2 Coal Mine. Using existing gas-geology data in coal mine and other data from test in laboratory and observation in underground mine, the distribution characteristics of magma and the relations about metamorphism of coal bed, deformation of coal bed, gas-generating conditions, gas-preserving conditions with magma intrusion are analyzed. The conclusions are that magma intrsion improved metamorphic grade, formed advantageous gas-generating and gas-preserving conditions, deepened deformation of coal bed and had important control role to form deformed coal in Ⅲ₃ coal seam of Xuandong No.2 coal mine.