Abstract: The gas permeance of oxygen and carbon dioxide for four kinds of barrier plastic films were investigated by a differential-pressure method and/or an equal-pressure method. The effects of temperature, film type and thickness and relative humidity on the oxygen and carbon dioxide gas permeability of the films were analyzed, and the oxygen transmission rates obtained from the differential-pressure method and equal-pressure method were comparatively investigated. The results indicated that there was a remarkable influence of temperature on the oxygen and carbon dioxide gas permeance of PET film with thicknesses of 12 μm and 25 μm, PET/Al film with a thickness of 12 μm and PVDC film with a thickness of 25 μm. These three types of films showed a rise of gas permeance with an increasing of temperature. Moreover, the logarithmic values of gas permeance of the barrier plastic films are linearly relative to the reciprocal of thermodynamic temperature. The gas permeability of oxygen and carbon dioxide for the barrier plastic films are quite different in a descent order of the PET film with a thickness of 12 μm > the PET one with a thickness of 25 μm > the PVDC one with a thickness of 25 μm are smaller > the PET/Al one with a thickness of 12 μm. The ratios of gas transmission rate of carbon dioxide to oxygen for the barrier plastic films are all more than four times compared to the original ones. Therefore, the four types of barrier plastic films all possess an excellent barrier property and permselectivity.