High-voltage p-i-n diodes for space applications are sensitive to single event burnout (SEB), which may cause the failure of the entire electronic system. This article describes the SEB failure mechanism of high-voltage p-i-n diodes with field limiting rings (FLRs) termination structure, based on the electro-thermal coupled transient simulation model in the Sentaurus TCAD simulator. The simulation results show that the catastrophic failures result from the intense local heating at the edge of the main junction, because the high electric field strength at this region induces strong impact ionization of the charge carriers. The strike at the edge of the main junction shows the strongest sensitivity to SEB since the energetic particle-induced carriers are deposited exactly at the high electric field region. Then, a novel SEB hardening technique of localized carrier lifetime control at the edge of the main junction region is proposed based on the analysis on the failure mechanism. Our simulation results demonstrate that the reduction of the localized carrier lifetime can alleviate the peak electric field and reduce the local heat accumulation, thereby improving the SEB performance of high-voltage p-i-n diodes.