Copolymerization of propylene and ethylene and terpolymerization of propylene, ethylene, and 1-butene were carried out to compare the characteristics of diether-and phthalate-based Ziegler-Natta catalysts in a reaction system of pilot scale. The ethylene incorporation with the diether-based catalyst was higher but the 1-butene incorporation was lower compared with those of the phthalate-based catalyst. In the case of copolymers from the diether-based catalyst, melting behavior, determined through differential scanning calorimetry (DSC), showed a distinct shoulder peak and lots of nuclei were formed during crystallization. The diether-based catalyst led to polymers having blockier ethylene sequences compared with those of the phthalate-based catalyst; the highly crystallizable fraction (HIS) containing blockier ethylene sequences was produced with the diether-based catalyst. These results seem to be the result of regio-irregular characteristics of the diether-based catalyst.