Abstract: By matching film permeation for O₂ and CO₂ with the respiration rate of fruits and vegetables，a mathematical model for modified atmosphere packaging(MAP) was established in this paper. On the basis of the in meodel the model the in respiration rate of tomato was determined by parameter estimation method. The new method that could be used in the whole storage period including steady and unsteady state was superior to the traditional method and respiration rate computed was closer to the real one in MAP. In addition, the changes of gaseous concentration and volume were simulated, which provides a reference for designing and controlling the MAP of fruits and vegetables.