Abstract: Wire breakage by lightning stroke is serious power safety accident of coal mine and threasts safety production of coal mine directly.The paper introduced reasons of wire breakage accident by lightning stroke, analyzed lightning current and thermal effect of short-circuit current in phase to phase induced by lightning current and mechanism of wire breakage by lightning stroke,gave results that the imperfect grounding system was indirect reason of wire breakage accident by lightning stroke and short-circuit current in phase to phase induced by lightning stroke was direct reason of wire breakage.At last it proposed technical countermeasures to prevent lightning stroke accident combining with actual power line.