Abstract: The thermal simulation analysis of the chassis is very important to improve the heat dissipation reliability of airborne radar electronic equipment and ensure the stable and reliable operation of the equipment. Detailed simulation calculation of the airborne chassis with complex structure and many plug-ins means a large number of grids, which can result in waste of computing time and resources. In this paper the system level and board level simulations of the chassis are carried out using Zoom-in function of Icepak software respectively. The overall temperature field, flow field and temperature distribution of key components of the chassis are obtained. At the same time, the temperature characteristics at different flight altitudes are studied with this method. This method can improve the simulation calculation efficiency and provide a new idea for optimal design of chassis heat dissipation.