Five different least-squares curve-fitting methods proposed by Antoon and Haaland were applied to the infrared quantitative analysis of multicomponent composition in various fiber blends and were compared with each other. The spectral region and threshold value for each blend were suggested to obtain accurate results. More accurate results could be obtained by methods I-III for all fiber blends than by methods IV and V. It could be considered that errors in measured spectra consist mainly of random noise error for all fiber blends.