Abstract: In order to realize the accurate source control of gas in the mining face of a mine in Tangshan, based on the stable carbon isotope analysis technology, the linear mixed gas source calculation model was used to quantitatively analyze the sources and proportions of mixed gas at different locations of the mining face, and the gas flow model of the mining face and goaf was constructed to simulate and analyze the spatial volume fraction distribution and change of gas in different coal seams, and to reveal the dynamic migration law of gas in the overlying coal seam and the coal seam. The results show that the carbon isotope values of CH₄ in the coal seam and the overlying coal seam are −68.02% and −77.91%, respectively. The gas contribution ratios of the coal seam at the upper corner of the mining face, the return air roadway at 30 m from the working face, and the return air side of the goaf at 10 m and 40 m from the working face were 76%, 67%, 59% and 81%, respectively. Under the influence of air leakage diffusion and fracture distribution, the coal seam gas showed a dynamic migration law of cross-layer flow and accumulation to the return air side, and the gas volume fraction increased with the inflow of overlying coal seam gas.