We have investigated the effects of proton irradiation on the subsequent time-dependent dielectric breakdown (TDDB) lifetimes of partially depleted (PD) SOI devices. Our results show that the TDDB lifetimes of the devices increased after proton irradiation and the amplitude increased with the intensification of the total ionizing dose (TID) damage. Moreover, the radiation-induced leakage currents (RILC) and the TDDB lifetimes of the irradiated devices by protons were dependent on TID damage but independent of energy of protons. We interpreted these results and mechanisms in terms of the effects of radiation-induced traps on the stressing current during the reliability testing, which may be significant to further expand the understanding of the radiation effects of the devices used in the space radiation environment.