Abstract: In order to study heat dissipation performance and the influencing factors of nuclear safety DCS chassis, this paper establishes a finite element model of a nuclear DCS chassis and carries out thermal simulation analysis. The research results show that the maximum temperature of U1 chip at the stable stage is 90 ℃, which is basically consistent with the actual measured temperature of 87.9 ℃. Therefore, the finite element model established in this study is effective and reliable. The surface temperature of the chassis is influenced by the function modules installed inside. The higher the thermal power consumption of the functional modules is, the higher the surface temperature is. At the position of the same function module, the temperature at the top surface of the chassis is higher than that at the bottom surface. In the state of natural convection, air flows in from the bottom surface and out from the top surface, and the air flow velocity at the top surface is greater than that at the bottom. Furthermore, by changing heating method, ventilation rate, air intake method, air volume and other factors to study the effect on heat dissipation performance of the chassis, the results show that the best thermal transmission path starts from the chip to the thermal pad, and then the heat transfers to the finned shell and finally to the chassis. Compared with natural cooling, the surface temperature of the key components reduces by 55.4 ℃. There is a positive correlation between the ventilation rate and the heat dissipation performance of the chassis. When the ventilation rate of the chassis increases, the temperature of the components shows an approximately linear decline. When the fan is installed above the chassis to absorb air, the temperature of the key components is 59.8 ℃. In contrast, when the fan is installed below the chassis to supply air, the temperature is 63 ℃, so the fan installed above is a better choice. The heat dissipation performance of the chassis is affected by the airflow of the fan. The larger airflow of the fan is, the better the heat dissipation performance of the chassis is.