Ambient temperature changes will affect the absorption efficiency of CO2 for infrared light.To improve the measurement accuracy of non-dispersive infrared (NDIR) CO2 gas sensor,a constant temperature CO2 gas sensor system based on incremental PID algorithm is designed.First,ANSYS FLUENT software was applied to simulate the thermal distribution inside the sampling chamber under constant temperature control to verify the feasibility of constant temperature control.Then,a constant temperature control system based on PI heater was designed.The experimental results show that the measurement error of the CO2 gas sensor proposed in this paper at a constant temperature of 40℃ is less than ±60 ppm in the range of 0~2000 ppm gas concentration.This result has certain reference value for the development of high-performance gas sensors.