The performance of optical gas sensors is greatly affected by the gas chamber structure. However, there are few researches aimed at improving the optical gas sensor by improving the structure of the gas chamber. Improving the utilization of chips is crucial to alleviate the global shortage of semiconductor chips and low-carbon environmental protection. In this study, a three-ellipsoidal gas chamber optical sensor with non-dispersive infrared technology is designed to improve chip utilization and satisfy the high performance detection requirements. The proposed sensor can simultaneously detect CO₂, SO₂, and CO. Furthermore, the optical performance of the gas chamber is studied. The results of the optical path, finite element, and Monte Carlo simulations clearly show that 91% of the energy is concentrated on 23% of the receiving surfaces, which effectively overcomes the problems of short optical path of the direct structure gas chamber and low luminous flux on the photosensitive surface (the optical path length increases by 25%, and the luminous flux increases by 40 times). Moreover, the problem of low luminous flux of the multi reflection structure (approximately 117 times) is mitigated. The signal-to-noise ratio distribution is 10-100 times that of the multireflection and direct reflection. Therefore, the proposed three-ellipsoidal gas chamber structure is of great significance for manufacturing high-end multicomponent combined gas sensors.