The IR spectra of cotton, PET, nylon 6, viscose rayon, polyproplene, acrylic and acetate rayon were obtained by using a FTIR spectrometric method. All these spectra were weight-normalized to a sample weight of 2 mg. The theoretical weight-normalized spectra of cotton/other fiber [A] at various blend ratios were obtained by the method as follows: the normalized cotton spectrum was multiplied with the scale factor, FC which was the corresponding value to the blend ratio of cotton. The same method as above was applied to the fiber(A) using the scale factor FA. Then the two spectra were added to produce the theoretical spectrum of the cotton/A fiber with that blend ratio. The peak-characterization data of these the theoretical IR spectra of cotton blends at various blend ratios could be well offered for qualitative analysis of cotton blends.