Abstract: Water vapor transmission rates of barrier plastic films were investigated at different temperatures and relative humidity by electrolytic and infrared detection sensor methods. Effects of temperature and film type on the water vapor permeability were analyzed, and the experimental results obtained from the electrolytic and infrared detection sensor methods were compared. The results indicated that PET film with a thickness of 12 μm presented greater water vapor permeability than that with a thickness of 25 μm. PET/Al film with a thickness of 12 μm and PVDC film with a thickness of 25 μm exhibited smaller water vapor permeability than that of the two PET films. The water vapor transmission rates increased with an increase in temperature for these four barrier plastic films. However, the temperature had less effect on the water vapor transmission rates of PET/Al film with a thickness of 12 μm and PVDC film with a thickness of 25 μm, and there was a linear relationship between the logarithm of water vapor transmission rate and the reciprocal of thermodynamic temperature. Test results obtained from the infrared detection sensor method were greater that those from the electrolytic detection sensor one. The difference between these two test results for PET/Al film with a thickness 12 μm and the PVDC with a thickness 25 μm was larger than those for PET films with thicknesses of 12 and 25 μm.