Abstract: Single-event gate rupture (SEGR) and single-event burnout (SEB) are the significant radiation threats from heavy ions due to the high applied gate voltage. The singleevent burnout effect on radiationhardened highvoltage SOI NMOS was reported. The hardened layout and ptype ion implantation process were developed to enhance the hardened structure against SEB effect, and the critical device parameters were designed and chosen according to electrical specifications. The SEB effect was studied in detail based on both simulated and experimental results. The experiment data demonstrate that the radiationhardened device achieves a high drain voltage of 24 V under singleevent irradiation with a linear energy transfer (LET) threshold value of 83.5 MeV·cm2/mg.