Abstract: In order to study the characteristics of heat trace of car body metal panel in the fire, on the basis of thermal analysis of the car body panel paint layer, the muffle furnace was selected to simulate the ideal radiation condition of the fire,and the influence of radiation temperature on the heat trace of the car bodies metal panel was studied. The results show that when the temperature rises, the surface paint layer of the metal face plate gradually falls off, when the temperature rises to 700℃, the surface paint layer basically falls off completely. When the temperature rises to 800-1000℃, some of the oxide layers of the metal face plate fall off, and the two sides of the metal surface plate bulge up, the whole is more brittle. The microstructure gradually changes from ferrite to network and acicular cementite from low temperature to high temperature.The Fe content gradually increases, the carbon content gradually decreases and tends to be stable, the microstructure thickness and hardness gradually decrease, and the temperature increases to 800℃. The above research results provide a basis for determining the direction of fire spread, the location of fire and the point of fire origin in vehicle fire investigation.