Aiming at Yangchangwan lignite, Shengli fat coal and Yangquan anthracite, the topological structure of raw coal pore space was reconstructed based on X-ray CT scanning technology. And the THM coupling experimental platform for methane displacement by gas injection of loaded raw coal was established, and the experiment of CH4 displacement by CO2 injection in raw coal under different conditions was conducted. Results show that: the porosity development degree, spatial distribution and connectivity of YCW lignite, SL fat coal and YMY anthracite become worse in turn. The CO2-ECBM process in raw coal goes through three stages: the replacement is dominant in the early stage; the replacement, carrying and dilution coexist in the middle stage; the carrying and dilution are dominant in the later stage. Stress and gas injection pressure can significantly affect methane displacement efficiency, and the topological property of coal pore is an important influencing factor. However, the strong adsorption of YMY anthracite can improve the methane displacement defect caused by the lack of seepage channel to a certain extent.