The invention provides a self-adaptive infrared gas detecting device and method, and relates to the technical field of infrared detection. The device comprises light source modules, open air chambers, self-adaptive processing units and a main control unit. Both a first light source module and a second light source module are used for generating near-infrared and middle-infrared light-wave signals and outputting the light-wave signals. Both a first open air chamber and a second open air chamber are used for storing to-be-detected gas and converting the infrared light-wave signals into electric signals. Both a first self-adaptive processing unit and a second self-adaptive processing unit are used for self-adaptive interference suppression of the signals absorbed through the air chambers and for outputting the processed signals. The main control unit is used for receiving and treating the signals after self-adaptive interference suppression, and the concentration of the to-be-detected gas is determined according to the result and a relation curve of "concentration-reference specific value". The concentration of gas under a complex environment and interference can be accurately measured.