Abstract: For problem of large measurement error of infrared methane sensor with reflective gas chamber, a new direct gas chamber was designed based on spectrum absorption principle of infrared light and non-spectroscopic detection technology. The infrared gas chamber achieves detection of volume fraction of methane gas by using external circuits combined with silicon semiconductor chip infrared light source, dual-channel infrared detector and midplane of gas chamber with certain length, and choosing GaF2 as window material of the light source and the detector. The test results show that the largest measurement error of the infrared methane sensor with direct gas chamber is only ±0.05% in the CH4 volume fraction range of 0～2.5%.