Abstract: Benzene homologues, including compounds such as benzene, toluene, and xylene, have become key pollutants of concern in food, drug, and environmental safety cases due to their significant carcinogenicity and ecotoxicity. Accurately tracing the source of these pollutants is of great significance for case handling and environmental pollution control. However, traditional component analysis methods, such as GC-MS and HPLC-MS, have limitations in traceability capabilities, and there is an urgent need to develop more discriminative technical approaches. Stable isotope ratio analysis technique exhibits unique advantages in forensic science and environmental traceability due to its ability to reflect the source and transformation processes of substances. In this study, an analytical method based on gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) was established for determining the stable carbon isotope ratios (δ¹³C) of benzene homologues, and its applicability in the source differentiation of benzene homologues was evaluated. This study systematically optimized the key experimental parameters in GC-C-IRMS analysis. In terms of chromatographic conditions, by comparing different initial temperatures (35 ℃ and 40 ℃) and backflush times, the optimal temperature program was determined as follows: maintain the initial temperature at 35 ℃ for 2 min, then increase to 80 ℃ at a rate of 5 ℃/min and maintain for 2 min, and finally increase to 150 ℃ at a rate of 10 ℃/min and maintain for 2 min. In terms of the injection mode, a 10:1 split ratio was shown to ensure good peak shape and stable isotope ratios while avoiding solvent interference. The optimal injection concentration range was further determined to be 300-600 mg/L. Within this range, the standard deviation of δ¹³C values is less than 0.20‰, meeting the requirements of high-precision determination. Method validation indicated that the intra-day and inter-day precision (SD) for the determination of δ¹³C values of benzene homologues are all less than 0.3‰, meeting the analytical standards for stable carbon isotope determination. This study also investigated the matrix effect and selected soil and cloth pieces as typical environmental matrices for spiked recovery experiments. The results showed that the matrix has a relatively small influence on the δ¹³C values of benzene homologues (the differences are all less than 0.3‰), indicating that this method is reliable for the analysis of actual complex samples. This method was applied to measure the carbon isotope ratios of benzene, toluene, m-xylene, 1,2,4-trimethylbenzene, and 1,2,3,5-tetramethylbenzene from three different sources for tracing their origins. The δ¹³C values of the five benzene homologues are −31.81‰-−30.66‰, −27.57‰-−23.88‰, −28.13‰-−27.04‰, −29.11‰-−28.74‰, and −31.00‰-−30.08‰, respectively. Based on the carbon isotope characteristics and one-way ANOVA results, effective differentiation of these benzene homologues from different sources was achieved. This study systematically establishes a GC-C-IRMS method suitable for the simultaneous determination of δ¹³C values of multiple benzene homologues and verifies its application potential in source identification. It offers a scientific reference for identifying the sources of benzene homologue pollution.