The invention belongs to an infrared gas sensor with low energy consumption within the range of gas explosion-proof detection device for mining safety. The infrared gas sensor is mainly composed of an absorbing cavity, a light source and an infrared detector, wherein, the adsorbing cavity is composed of a big spherical mirror and a small spherical mirror; the big spherical mirror is fixed on a bracket above the small spherical mirror; the light source is arranged on the concave surface center of the small spherical mirror between two spherical mirrors; the small spherical mirror, the light source and the detector are fixed on a support; and the above components form a sensor module. The invention ensures that the light source and the detector conform to imaging relationship after light path folding, light imaged on the detector is in diffusion form so as to evenly distribute light on the detector, so that the signal-to-noise ratio of optical signals is improved. The invention fully utilizes optical energy, effectively lowers light source energy consumption, and ensures that the power consumption of the sensor is smaller than 90mw.