Abstract: A new method for computing film permeability coefficient under the condition closer to modified atmosphere packaging(MAP) was presented in this paper. The method was as follows: a series of film permeability coefficient values were tentatively set, and they were respectively put into the mathematical model of MAP, so gaseous concentration values could be computed respectively at sometime. When the square of difference between gaseous concentration value computed and its counterpart measured actually in MAP at sometime was the least, a tentative film permeability coefficient value was the needed one accordingly. The results showed that the film permeability coefficient value computed by the new method was closer to the objective film permeability coefficient than the one by other methods.