With the advancement of semiconductor and new-energy engineering, detecting hydrogen sulfide (H₂S) at extremely low concentrations has attracted increasing attention. To address challenges in trace H₂S measurement, this study integrates preconcentration with cavity ring-down spectroscopy (CRDS) and develops a preconcentration-CRDS system for detecting trace H₂S impurities. This paper systematically describes the selection of solid adsorbents, the system design, and the experimental protocols. First, based on the CRDS detection capability (0.5 μmol/mol H₂S), the evolution of H₂S concentration during the preconcentration process is investigated. Calibration experiments established a quantitative relationship between the maximum H₂S concentration during the desorption stage and the initial H₂S concentration in the sample gas. The results indicate that the preconcentration approach enhances the H₂S concentration by more than sixfold. The system performance, including reproducibility, detection limit, and long-term measurement stability, is analyzed in detail. The relative error of the maximum H₂S concentration across three experiments is 5.5%. The detection limit, defined as twice the zero-point noise, is approximately 36.8 nmol/mol. The stability, derived from Allan-variance analysis, is 0.4 nmol/mol. Finally, quantitative measurements of trace H₂S in CH₄, C₂H₆, C₂H₄, C₃H₈, C₄H₁₀, and CO are performed using the developed system. The H₂S content in C₄H₁₀ is the highest, at approximately 83 nmol/mol. In contrast, for CH₄ and C₂H₆, no H₂S desorption is observed during the desorption stage. Based on the production processes and experimental findings, potential sources of H₂S in different fuels are analyzed. Overall, the preconcentration-CRDS system demonstrated excellent performance for trace H₂S detection, offering a promising and innovative approach for monitoring ultra-low H₂S concentrations.