The isothermal crystallization curves of polypropylene over a wide range of temperatures were obtained by the inverse gas chromatography. The calculated velocity constants are in accord with those derived by other methods. The experimental data have been treated with Avrami's equation the crystalline index n equals to 2.1. The crystallinity and the melting point of this polymer were studied. The crystallinity are influenced by experimental conditions and the thermal history of the sample. The melting points of both a-and β-form have been found by this method. In case there are two crystalline forms coexisted in one sample

a higher value of crystallinity is obtained as compared with that by other methods.