In this paper, the spectra of PET films annealed under different conditions were measured by means of Fourier-transform infrared spectrometer. The infrared spectra reconstruction technology could be used for the quench least-square peak solution treatment of the 1340cm^-^1 band, which belongs to trans conformation mode. With the help of the 1454cm^-^1 band contributed by the quauche conformation and through multivariate linear regression analysis, the content percentage of the crystalline region trans conformation, the amorphous region trans conformation, and the amorphous region gauche conformation were obtained.

Key words: QUANTITATIVE ANALYSIS, INFRARED SPECTROPHOTOMETRY, POLYETHYLENE TEREPHTHALATE, CONFORMATION, FOURIER TRANSFORM, CRYSTALLINE REGION