In this paper,a dual-channel differential methane (CH₄) detection device based on min-infrared absorption spectroscop y is implemented by using the absorption characteristic of CH_4molecule in mid-infrared waveba nd and an infrared light source (IR55) with wide emitting spectrum.Through the differential processing o n the two output signals from the dual-channel detector (3.31μm and 3.9μm),the system noise can be removed effectively.Detection principle and structure are proposed,and the optical cha racteristics of the light source and the detector are analyzed.In order to improve light collection effi ciency and enhance absorption length,structures of spherical reflection mirror a nd open gas cell are optimized,whose radius is 20cm.Sixteen CH_4samples with different concentr ations were prepared,calibration experiment was carried out using the detection system,and the expression between concentration and two channel signals was derived.System e rror experiment indicates that the relative detection errors on the 16CH_4samples are less than 12.4%.At the same time,a 10h long-term concentration detection on the 5×10－4 CH_4sample indicates that variation range of the detected result is ±10%.Meanwhile,mathematical stat istics on the 10h results reveals that the standard derivation is 2.06×10－4,and the limi t of detection is estimated to be 6.18×10－4.