To address the limited Raman scattering area， which diminishes signal strength and detection sensitivity， this study enhances the Raman signal intensity and detection sensitivity through optical path optimization. Experiments investigating various reflection modes within the cavity and collection system angles examined the effects of the incident light's polarization state and dual-path collection on the Raman scattering signal. Utilizing the optimized parameters， a multi-pass reflective cavity system was developed. Using the Raman spectra of oxygen and nitrogen in air as reference signals， results demonstrated that the signal intensity with P-polarized incident light was 1.3 times greater than that with S-polarized light. Implementation of a dual-path collection system increased the total collected scattered light， thereby improving Raman scattering collection efficiency. The signal-to-noise ratio of the dual-channel collection system increased by 1.5 times for Channel A and 1.7 times for Channel B， enabling the detection of carbon dioxide in air. Furthermore， the device exhibited a strong linear correlation between signal intensity and gas concentration， confirming its capability for quantitative analysis.