Based on metal-oxide-semiconductor field effect transistor (MOSFET) microscopic mechanism of radiation damage, a relation between radiation induced increase in number of oxide hole-traps and post-irradiation threshold voltage drift is proposed. Then, Based on MOSFET microscopic mechanism of1/f noise generation, a quantitative relationship between pre-irradiation1/f noise power spectral amplitude and post-irradiation threshold voltage drift is founded, which accords well with the experimental results. This relationship shows that pre-irradiation1/f noise power spectral amplitude is proportional to post-irradiation threshold voltage drift, which can reflect the degradation of latent defect in MOSFET. So, this modal is helpful to characterize the quantity and severity of latent defect in MOSFET by using1/f noise parameters.