In agricultural harvesting operations, agricultural fires can be induced due to various human or natural factors. Agricultural fires pose a great threat to agricultural production and the safety of life and property, so it is imperative to accurately monitor agricultural fires. At every stage of fire, gas can be produced. So gas sensors have been developed rapidly in the field of fire detection. In case of a fire, the burning of crops will produce a large amount of carbon monoxide (CO) and carbon dioxide (CO₂), which will lead to a rapid increase in the concentration of CO and CO₂ in the air. Real time monitoring of changes in the concentration of CO and CO₂ can give an alarm. A gas sensor based on Non-Dispersive Infrared (NDIR) has the advantages of high integration and low cost, which is conducive to miniaturization design, on-site detection and commercial promotion. Therefore, many studies on NDIR gas sensors have emerged. However, the reported NDIR sensors only show good performance under laboratory conditions, but often do not perform well in low temperature environments. The main reason is that the internal infrared thermoelectric detector is prone to temperature drift in low temperature environments, and it is difficult to work normally under low temperature conditions. In view of this phenomenon, a small temperature control system is designed for the infrared detector, and is applied to a NDIR CO₂ detector. Then the detector can be maintained at 21 ℃ in a low temperature environment at -40 ℃. Finally the purpose of making the sensor work normally under low temperature environment is achieved.Firstly, the detection principle of the infrared gas detector is introduced, and the relationship between harmonic signal and gas volume fraction is determined according to Lambert-Beer law. The system structure of the detector is analyzed, which is mainly composed of an electrical module, an optical module, an upper computer monitoring module and a detector temperature control module. Under a low temperature environment below -20 ℃, the output signal from the detector has serious drift, which may even cause irreversible failure to the sensor. Then, the hardware circuit and software program of the temperature control system are designed according to the structure of the detector and the light source. The temperature signal collected by PT100 is converted into a digital signal through an analog-to-digital converter and is collected by the master controller. The sampling temperature is calculated to obtain the adjustment value, and then a heating film drive circuit is used to control the detector temperature. In the hardware part, the influence of the wire resistance on the temperature acquisition is eliminated, and a BUCK driver circuit is modeled. In the software program, both positive temperature and negative temperature are solved by different formulas, and the PID algorithm is improved. Finally, the temperature control system is integrated into the fire detector. Under the ambient temperature of -40 ℃, the temperature is controlled from an initial temperature of 20 ℃, and the response time to stabilize the detector temperature at 21 ℃ is 16 s. The stability of the temperature is 0.012 6 ℃ (1σ). The response time and stability meet the temperature control requirements in low temperature environments. Under the condition of temperature control, the sensor is calibrated, and the first harmonic amplitude ratio of the voltage signals from the absorption channel and the reference channel obtained from the gas calibration experiment and the concentration of the standard gas are exponentially fitted to obtain an exponential fitting curve, with a goodness of fit of 99.852%. The stability of the detector is tested for 25 min using pure nitrogen (N₂) sample, and the measured concentration fluctuation range is -28.128 76×10^-6~27.240 5×10^-6. Allan variance is introduced for sensor performance evaluation. When the averaging time is 0.25 s, the lower detection limit is 1.213 01×10^-6; when the averaging time is 114.75 s, the theoretical lower limit of detection can reach 4.822 5×10^-7. The experimental results show that the temperature control system can ensure the normal work of the fire detector in a low temperature environment, and has practical application value.