The single event effect of H-gate SOI NMOS devices in total dose ionizing are studied by means of numerical simulation. By analyzing the mobility degradation in the simulation process, the corrected mobility Lombardi model due to degradation at interfaces is obtained. As the simulated transfer characteristic curves of SOI transistor agree well with the experimental data, the single event effect of H-gate SOI NMOS devices in total dose ionizing is simulated by this corrected model. Results shows that the maximum drain currents of devices under the same conditions are slight increasing, but the transistors get a significant increase in the drain collected charge with increasing total dose level.