The work aims to compare the different permeation activities of various gases in packaging material and analyze factors that influence such activities, which provides reference for study of applicability of packaging materials and improving the separation effect of films. Gas permeability of O2, N2 and CO2 through BOPP, PET and PE film samples was tested respectively with differential-pressure method. Diffusion coefficients of the three gases were calculated with time-lag method and the solubility coefficients were obtained by calculating the gas permeability coefficient and diffusion coefficient. The results showed that the order of gas permeability coefficients and solubility coefficients was CO2＞O2＞N2 for all the three films, while diffusion coefficients were in the order of O2＞CO2＞N2 for BOPP and PE films, and O2＞N2＞CO2 for PET film. The ratios of permeability coefficients of CO2/O2 were 2.7, 3.8 and 3.7, while the ratios of permeability coefficients of CO2/N2 were 14.4, 25.0 and 14.3 for BOPP, PET and PE films, respectively. Diameter of gas molecule and its interaction with film molecules are the main factors that influence gas diffusion coefficient, while gas critical temperature and interaction between molecules are the main factors that influence solubil-ity coefficient. For gas permeation rate, from fast to slow, it is CO2, O2 and N2 in all the three films under combined action of diffusion coefficient and solubility coefficient. Among these three films, PET and PE have better separation effect for CO2 and O2, while PET has better separation effect for CO2 and N2.