The changes in chain conformation of uniaxially-drawn PET films, which had been annealed at 80-24$0^{circ}C$ with unrestrained and constant length conditions, were investigated by means of factor analysis and band resolution of their IR absorbance spectra. The presence of four absorbing components in the range of 1050-1010 cm-t was confirmed by factor analysis. And this result could act 2s a complement to the band deconvolution. Assuming that each absorbing spectrum was a Lorentzian distribution function, the result of band deconvolution showed that absorbance spectrum in the range of 1050-1010 cm-1 could be deconvoluted into four independent Lorentzian curves, i.e., 1043, 1025$pm$ 1, 1020$pm$ 1, and 1017$pm$ 1 cm 1. From the presence of 1025$pm$ 1 cm-1 peak, the intermediate phase, which had been proved to exist in indrawn PET film, was ascertained in drawn PET film in addition to amorphous and crystalline phase. The content of each phase was compared relatively with its integrated intensity. Crystalline phase increased but amorphous one decreased in their contents with an increase of annealing temperature. On the other hand, the intermediate phase increased as annealing temperature increased below the critical annealing temperature. There were a good linear relationship between the content of crystalline phase and density and a good correlation between the absorbance of 972 cm-1 and birefringence for the taut -annealed PET specimen.