Abstract: The influence of heating rate on the metallographic structure of JJC1-35 insulation piercing connectors with poor contact beads under different heating conditions was simulated by changing the heating rate under the metallurgical microscope with heating stage. The results show that the average grain range of the metallographic structure will increase with the increase of temperature, the grain intercept will increase with the increase of the heating rate, and the grain size will decrease with the increase of the heating rate. The pores of the metallographic structure gradually shrink with the increase of the heating temperature, and the shrinking speed increases with the increase of the heating rate. The study provides a more scientific basis for the identification of such fire physical evidence.