The working temperature of semiconductor laser in TDLAS (tunable laser absorption spectroscopy) technology directly affects the accuracy of gas concentration detection. The experimental results show that the multilevel integral separation PID control algorithm has advantages in improving the response speed of the temperature control system, improving the accuracy and stability of the system, and reducing the overshoot. The temperature control system has a temperature control accuracy of better than ± 0.03 ℃ in the temperature control range of 10 ~ 40 ℃, and reaches the set temperature within 148 s. The temperature control overshoot is less than 2.5%. The design meets the requirements of TDLAS gas concentration detection and lays a foundation for high-precision detection of gas concentration.