The invention provides a gas remote sensing detection device and a method. The gas remote sensing detection device comprises a light source, a beam splitter, a light deflection module, a gas pool, a first detector, a second detector and a processor, wherein the wave length of measuring light emitted by the light source covers gas to be detected and spectral lines of absorption of gas in the gas pool; the beam splitter is used for dividing the measuring light into a first light beam and a second light beam, and the first light beam penetrates through a region to be detected; the light deflection module is used for changing the advancing direction of the first light beam; the second light beam penetrates through the gas pool, and the gas pool contains gas with known concentration; the first detector is used for converting measuring light penetrating through the region to be detected into first electric signals and sending the signals to the processor; the second detector is used for converting the second light beam penetrating through the gas pool into second eclectic signals and sending the signals to the processor; the processor is used for adjusting the work parameter of the light source so that drifting of the light source corresponding to the first electric signals cannot exceed the standard and used for adjusting the inclination angle of the light deflection module relative to the incident first light beam so that interference among reflection light of the first light beam on a reflector in the region to be detected cannot exceed the standard. The gas remote sensing detection device and the method have the advantages of being high in accuracy, simple in structure, low in cost and the like.