Because the gas Raman scattering signal is very weak, the application of laser Raman technology in gas detection is limited. This study presents a method for enhancing the Raman signal for gas detection using multiple reflections and increased pressure. The air under normal pressure is used as the component to be measured, and the air under normal temperature and pressure is compressed into a closed sample tank by a pressure pump. The pressure in the sample tank is maintained at 0.1 MPa, 0.2 MPa, 0.3 MPa,…,1 MPa. The Raman spectral data of oxygen, nitrogen, and carbon dioxide in air (with wave numbers of characteristic peaks at 1552 cm^-1, 2333 cm^-1, and 1278 cm^-1/1386 cm^-1, respectively) are collected under the conditions of 10 different pressures and an integration time of 1 s. Variations in the characteristic peak with pressure are analyzed according to the four parameters of peak intensity, peak area, signal-to-noise ratio, and half-peak width. Results show that the signal-to-noise ratio is positively correlated with the pressure, which basically conforms to the logarithmic relationship. The signal-to-noise ratio increases by approximately 21 dB when the pressure increases from 0.1 MPa to 1 MPa. The peak intensity and peak area are positively correlated with the pressure and conform to the linear relationship. The central position of the characteristic peak is practically unrelated to the pressure, and the half-peak width changes little with pressure. Compared with the data of 1 MPa and 0.1 MPa, results also show that the oxygen characteristic peak expands to approximately 0.7 cm^-1. Therefore, increasing the gas pressure is a simple and effective means of enhancing the Raman signal. The Raman signal can be further enhanced based on multiple reflections.