Abstract: A gas composition analysis system based on Cavity-Enhanced Polarization-differential Raman Spectroscopy （CEPRS） was constructed. In this system, a high-finesse optical cavity was utilized to achieve significant intracavity laser power enhancement, thereby amplifying the Raman scattering signal intensity. Polarization-differential detection was incorporated to effectively suppress water vapor interference by exploiting the intrinsically high depolarization ratio of water molecules. The system was calibrated using certified reference gas mixtures, and quantitative relationships between the Raman scattering integrated intensity and the concentration of each component were established. Based on these calibration relationships, the analytical performance of the system was systematically evaluated. The results showed that, under an integration time of 600 s, the detection sensitivity for CO₂ was better than 0.5×10⁻⁶, and the relative uncertainty of the quantitative analysis for standard gas mixtures was better than 0.15%（k=1）. Under the same integration conditions, the detection sensitivity for trace H₂ was better than 0.17×10⁻⁶, confirming the capability of the system for highly sensitive trace gas detection. The system was subsequently applied to the measurement of laboratory ambient air and human breath samples. Simultaneous detection of major components, including N₂, O₂, CO₂, and H₂O, as well as trace H₂, was successfully achieved, demonstrating that the CEPRS-based approach enables multi-component synchronous detection across a wide dynamic concentration range. The experimental results further demonstrated that the system exhibits good repeatability and long-term operational stability. These findings indicate that the proposed CEPRS-based analytical system holds considerable potential for applications in environmental monitoring and breath-based medical diagnostics.