The effects of γ-ray irradiation on the subsequent time-dependent dielectric breakdown (TDDB) of partially depleted (PD) silicon-on-insulator (SOI) MOS devices were investigated. By testing and comparing the transfer characteristic curves, threshold voltage, off-state leakage current, the TDDB lifetimes and other electrical parameters of the NMOS and PMOS devices before and after irradiation, the effects of γ-ray irradiation on the TDDB reliability of the devices were analyzed. The results show that the positively charged oxide trap charges induced by γ-ray irradiation in the gate oxide layer affected the distribution of the internal barrier of the device, and reduced the height of the barrier of the electron transition. Therefore, the positive feedback effect of electron tunneling is enhanced and the TDDB lifetime of the device is reduced, resulting in a reliability degradation of the gate oxide of the devices.