In order to study the trace characteristics of multi-strand copper-clad aluminum conductor under the fault of over-current,copper-clad aluminum conductor conforming to the national standard was selected. By changing the preset current value,melting marks of copper-clad aluminum conductor at different degrees of over-current were prepared to observe the heating phenomenon and macroscopic trace characteristics of the conductor after heating. The analysis shows that the phenomenon of wire heating deformation is related to the current value,Only when the over-current multiple is between 2 and 4 times,the insulation can be burned in a large range,which can cause fire;in addition,the copper clad aluminum conductor with excessive current has and only produces molten beads at the first breakpoint. Since molten beads do not appear in the burn mark,short circuit or over-current fault will occur once molten beads are found in the fire.