Abstract: OPGW is an important element of power electrical system.It is not only used for ground wire against lighting strike to protect transmission line, but also as fiber optic cable to transmit information. OPGW optical cable of a 500 kV transmission line in China Southern Power Grid was broken. during operation causing multiple service channels to be interrupted affecting the stable operation of the power grid. In order to find out the cause of the fracture, The fracture causes of OPGW optical cable are analyzed by means of macro morphology observation, SEM fracture micro morphology observation. In this article we find out the inner and external reasons of lightning-caused OPGW strand breakage. we also discuss how to improve OPGW performance against lightning strike in some aspects such as transmission line design, the OPGW types selection and OPGW maintenance. Some preventive measures also put forward for reference in the paper.