The body current lowering effect of 130nm partially depleted silicon-on-insulator (PDSOI) input/output (I/O) n-type metal-oxide-semiconductor field-effect transistors (NMOSFETs) induced by total-ionizing dose is observed and analyzed.The decay tendency of current ratio of body current and drain current Ib/ Id is also investigated.Theoretical analysis and TCAD simulation results indicate that the physical mechanism of body current lowering effect is the reduction of maximum lateral electric field of the pinch-off region induced by the trapped charges in the buried oxide layer (BOX).The positive charges in the BOX layer can counteract the maximum lateral electric field to some extent.