Abstract: High flux engineering test reactor(HFETR) is a multipurpose test reactor that undertakes numerous important irradiation and production tasks. Voltage sags caused by lightning strikes can lead to unplanned shutdowns, disrupting the normal progress of the reactor′s research and production plans. This article first conducts a statistical analysis of lightning strike shutdown events, then proposes two voltage sag mitigation schemes, followed by a comparison of the advantages and disadvantages of each scheme. Finally, it concludes that adopting an external power failure protection signal with an additional delay can enable the HFETR to effectively cope with voltage sags caused by lightning strikes.