Abstract: To achieve accurate quantitative analysis of mixed gas sources and dynamic characterization of the contribution rates of each gas source, coal samples from different seams and mixed gas samples were collected in this study. A systematic investigation was conducted by integrating physicochemical property testing of coal, carbon isotope analysis, and an end-member mixing model. The results indicate that tectonic coal exhibits a more developed pore structure and a higher degree of aromatic structural ordering compared with raw coal. No. 8 coal seam is dominated by macropores, facilitating seepage under low-pressure conditions, whereas the No. 9₂ and NO. 9₃ coal seams are dominated by micropores, showing strong adsorption capacity and thus providing the structural basis for gas source tracing. The δ¹³C values of methane in No. 8 coal seam range from −57.77‰ to −56.86‰, displaying typical biogenic characteristics. In contrast, the median δ¹³C values of methane in the No. 9₂ and No. 9₃ coal seams are −56.94‰ and −55.74‰, respectively, showing heavier isotopic signatures and inter-seam genetic differences. Quantitative analysis based on the end-member mixing model reveals that methane in the mixed gas is dominated by coalbed gas, with the contribution of the No. 9₂-9₃ coal seams generally exceeding 40% and reaching over 97% in some cases, among which No. 9₂ coal seam contributes more prominently, while No. 8 coal seam serves as a secondary source.