Abstract: The fire melted mark, primary short circuited melted mark and secondary short circuited melted mark of the copper wire were prepared by simulation experiments. The micromorphology of these marks were observed and the microscopic characteristics was summarized. The results show that no holes existed at fracture of the fire melted mark. The microscopic characteristics of the primary short circuited melted mark before and after being treated at high temperature was the same; uniform and fine holes existed at the fracture and the fracture presented an oval pattern. The holes at fracture of the secondary short circuited melted mark varied in size and the fracture presented a honeycomb pattern.