The conformational ordering in spherulites of isotactic polypropylene during growing process is studied with in situ infrared microspectroscopic imaging. A comparison between the intensity distribution of bands representing crystal and conformational ordering indicates that large concentration of conformational ordered segments exist in the growth boundary region of spherulites, which suggests that conformational ordering takes place before packing into crystal lattice in the growth boundary layer. The width of the growth boundary layer is sensitive to temperature but keeps relative constant during isothermal crystallization process. Though the interchain organization of the conformational ordered segments is not clear yet, conformational ordering in the growth boundary layer is assigned to be a preordering step of crystallization.