Aiming at the heavy weight and inconvenience when carrying and installing copper earthing wires on the UHV transmission lines, this paper proposes a lightweight method for UHV earthing wire conductor by using the copper clad aluminum(CCA) as composite materials. Firstly, theoretical calculations and experiments of the fusing current in a short time for copper and CCA material are performed. Then, the transient electro thermal coupling process of the earthing wire shortcircuit of typical 1 000 kV doublecircuit line is simulated. The results show that the theoretical value of the earthing wire conductor's fusing current corresponds with the test value on condition of the conductor cross section greater than 4 mm2 as well as melting time less than 1.5 s. The CCA10 earthing wires present 71% cross section increase and 36.2% weight reduction compared with copper wires. In the case of singlecircuit poweroff maintenance of 1 000 kV doublecircuit line, it is suggested to select 50 mm2 copper wire or 95 mm2 CCA10 wire, and the CCA earthing wire has greater safety margin.