Photoacoustic spectroscopy has been widely used in gas detection because of its high sensitivity, strong reliability, and fast response. Because the high-reflectivity coating on the inner walls of integrating spheres can greatly increase the optical path, integrating spheres are often adopted in absorption spectroscopy to improve detection sensitivity. In this paper, an integrating sphere is applied to gas detection by photoacoustic spectroscopy. With the integrating sphere gas cell as the absorption pool, an aluminum tube is attached to the sphere as a resonant cavity to form a coupled acoustic system. The actual resonance frequency of the system is obtained through simulations and experiments. At this frequency, the LED light source is modulated, and the gas is stimulated to generate photoacoustic signals. Embedded technology is integrated to collect the signals of the two microphones on the ball and at the end of the aluminum tube for data processing, analysis, uploading and display. NO₂ gas is employed in the experiments and the experimental results show that the signal values at the end of the aluminum tube can effectively invert the NO₂ gas concentration, and the minimum detection concentration (volume fraction) is 3×10 ^-6.