Tunable diode laser absorption spectroscopy (TDLAS) is often used for gas concentration detection. However, the change of ambient temperature affects the absorption line strength, absorption line type, and gas molecular number density and thus results in measurement errors. We designed a high precision temperature control box to control the ambient temperature where the gas cell is located. First, the effects of parameters such as the shape of the temperature control box, thermoelectric cooler position, and airflow vector on the temperature distribution inside the box were simulated using the CFD simulation software. Second, with the help of the simulation results, we optimized the design and processing of the temperature control box. Finally, we completed the fabrication of the temperature control box which can provide a uniform and stable temperature environment for the gas cell. The temperature adjustment range of this box is 32-50 ℃, the control accuracy can reach 0.01 ℃, and a long-term stability is realized. Temperature stability was verified by the CO₂ gas concentration detection experiment. Therefore, using CFD simulation to optimize the parameters of the temperature control device, one can obtain a stable and uniform temperature control system, reduce the influence of ambient temperature on the measurement results, and effectively improve the accuracy and stability of gas concentration measurements.