In order to reduce the ambient temperature and the non-uniform temperature field formed by the internal heating elements, the imaging performance of the infrared thermal imager was affected. The finite element model of the infrared thermal imager was established by Proe and Ansys ICEPARK. The black anodizing and blasting treatment on the surface of the infrared lens enhanced the radiation heat transfer, and the fan was used to enhance the convection heat transfer to ensure the heat dissipation in the high temperature environment. The thermal resistance was designed for temperature rise, and the internal temperature distribution and infrared lens temperature distribution of the infrared thermal imager under different temperature environments were simulated and analyzed. The infrared thermal imager in thehigh and low temperature chamber was used to observe the target in the collimator. The image quality of the graph verified the efficiency of the temperature control design. The results show that the temperature control circuit board can control the temperature of the fan and the thermal resistance. When the ambient temperature drops to 0 ℃ and rises to 30 ℃, The temperature control system is activated to make the temperature of the infrared thermal imager optical system normal, and the imaging quality of the infrared thermal imager is ensured.