Abstract: The relation between partially depleted SOI NMOSFET total dose radiating effeot and bias status was experimentally studied.The experimentoll results showed that TG（Transition Gate）is the worstcase bias.And next,MEDICI simulation and a numerical model are utilized to simulate the electric field inside the buried oxide and fraction of hole capture,respectively.Simulation results explained experimental results reasonably.High electric field and high fraction of hole capture in buried oxide are the main reasons why TG is the worst-case bias.