Based on metal-oxide-semiconductor field effect transistor (MOSFET) noise theory of carrier number fluctuation and mobility fluctuation， a quantitative mathematic model between pre-irradiation 1/f noise parameters and post-irradiation threshold voltage drift due to oxide traps and interface traps is established. It agrees well with the experimental results. This model shows that 1/f noise in MOSFET is priginates from the random trapping/detrapping processes between oxide traps and the channel， which causes fluctuations in both the number and the mobility of channel carriers. So pre-irradiation 1/f noise magnitude is directly proportional to post-irradiation oxide-trap charge. The results not only explain the correlation between MOSFET pre-irradiation 1/f noise power spectral density and radiation degradation in theory， but also provide the theory for forecasting MOSFET radiation-resistant capability.