Abstract: Low metamorphic coal mining in our country, the author of this paper is difficult, the problem of high cost, using electric heating method of lignite in low metamorphic coal microstructure was studied, using fine microscopic CT systems respectively looked at 25 ℃, 300 ℃, 400 ℃, 500 ℃ after micro pore of lignite by using 3 d digital core technology established a three-dimensional pore fissure skeleton diagram, after high temperature, sample pore and fracture porosity are obvious increase, which, after 400 ℃, pyrolysis, sample pore development completely, sample porosity appear spurt, visible, continuous high temperature, the pyrolysis of organic matter, Accelerated pore development. The experimental data provide a reference for the mining of low metamorphic coal seam.