Abstract: The coal seam heat injection is a new type of coalbed methane extraction method proposed in recent years. In order to get the effect of coal seam heat injection on the production of coalbed methane, it is necessary to study the variation of coal permeability under the condition of heat injection. Based on the geometric model of Warren-Root and the elasticity theory, the coal permeability model is established and studied by numerical analysis. Finally, the variation of coal permeability is obtained around the heat injection drilling hole under the condition of heat injection, which provided the foundation for the analysis of multi-field coupling model of coal seam heat injection.