The direct determination of crystallinity of polypropylene fiber by inverse gas chromatography has been studied．The columns were pa~ked with physical mixtures of GC support and fiber seetionS in powder form．which was obtained by cutting the fiber samples with a pair of scissors．This treatment eliminates the need for solution coating or heating of the column packing，which may influence the erystallinity in some degree．We used a column with 3 mm O.D. to hasten the temperature equilibrium． so that the reliability of the extrapolated term of Guillet's equation．which was used to calculate the crystallinity，could be improved．The values of crystallinity obtained by this method are not influenced by such factors as various probe molecules，the length of column and the content of polymer．The results of eight samples obtained are consist-net with those detcrmined by X-ray and density methods．