The PVC insulated flexible cords are used mainly as power supply cords of electric appliance. This electric wire is a stranded wire consisted of dozens of strands. In case stranded wires are disconnected by mechanical stress, it weakens electrically. Finally, the over current flows through stranded wires, and electrical fire occurs. In this study, we analyzed the melting properties of strands by over current, such as melting process, melting current and melting time. And we analyzed that quantity of heat for melting, a cross sectional structure, and surface structure by optical microscope and SEM. As analysis results, melting time decreased as melting current increased. And quantity of heat for melting was low, too. From the cross sectional structure of melted wire, when a melting current low and melting time long, it was found that the dendrite structure grew. However, the dendrite structure is hard to grow because growing time is not enough when a melting current high and melting time short.