Abstract: The failure phenomenon of the junction box used for photovoltaic modules in a large-scale photovoltaic power station was investigated. This investigation involved the visual inspection of the junction box, analysis of its voltage-current (I-V) characteristics, and further dissection testing and analysis. Ultimately, the burn marks were discovered on the protection ring position of the diode's surface after dissection. The failure of the junction box was attributed to diode breakdown induced by lightnin strike.