In this paper the characteristics of isothermal and isochronal annealing for post-radiated MOS transistor were studied. The results show that 100℃ isothermal a nnealing is the most effective treatment, while the time of isochronal annealing is the shortest. Secondly, the recovery of threshold voltage under the +5V bias is the fastest and biggest, compared to that under 0V and float bias. These predictied results by using isochronal annealing data were compared with the ex periment curve obtained from isothermal annealing, and the agreement is good.