Abstract: Injecting carbon dioxide to replace gas is a key means to improve the efficiency of deep low-permeability coal seam gas extraction. It can not only enhance methane recovery rate, but also achieve geological storage of carbon dioxide, with both economic and environmental value. In order to explore the law of injecting carbon dioxide into coal seams for gas displacement, this paper proposes a thermal fluid solid coupling model that considers binary gas permeation, diffusion, competitive adsorption, and coal deformation. With the help of COMSOL numerical simulation software, the dynamic changes of carbon dioxide concentration, coal permeability, and temperature under different gas injection pressures and injection production intervals are systematically studied. The gas recovery rate and carbon sealing stock under different parameters are also studied to evaluate the displacement effect. The reliability of the model is verified through on-site process experiments. The results show that the average error between the numerical simulation results of the proposed thermal fluid solid coupling model and the physical experimental results is within 8%, which can effectively study the law of carbon dioxide displacement of gas; The increase in gas injection pressure and injection production spacing can significantly enhance the diffusion ability of carbon dioxide in coal, intensify coal deformation, and make permeability and temperature fluctuations more pronounced; The injection pressure increased from 0.5 MPa to 2.5 MPa, and the CH ? recovery rate and carbon seal stock increased by 10.47% and 387.00%, respectively. The carbon seal stock was more sensitive to the injection pressure response; When the injection production spacing increased from 3m to 7m, the two increased by 48.34% and 9.19% respectively, and the CH ? recovery rate was more sensitive to the injection production spacing; Engineering should optimize injection and production parameters based on actual goals. If gas production is the main focus, priority should be given to increasing the injection production spacing; If carbon dioxide storage is the main approach, priority should be given to increasing the injection pressure. Further on-site process experiments have confirmed that increasing the gas injection pressure and injection production spacing can effectively improve the gas extraction speed and yield. The research results of this article provide important theoretical support for efficient extraction of low-permeability coal seam gas.