Abstract: A simple mathematical model about the dynamic variation of alveolar oxygen partial pressure during explosive decompression is established in this paper. With this model the process of alveolar oxygen pressure change during explosive decompression process is simulated with molecular sieve oxygen generating system(MSOGS). The effects of concentration of supplying oxygen and the flight altitude is analyzed. The predicting and experimental results are in good agreement. This model provides an easy approach to calculate the critical time for the explosive decompression process. It is helpful for design of life-support equipment and medical watch of high altitude flight.