Disclosed is a method of preparing a highly transparent polypropylene amprising a step of prepolymerizing an alpha-olefin and a vinyl cyclic saturated hydrocarbon in the presence of a Zegler-Natta catalyst and an external electron donor, wherein a step of adding and pre not polymerizing the alpha-olefin is followed by a step of adding and prepolymerizing the vinyl cyclic saturated hydrocarbon. The method provides polypropylene having superior tacticity and transparency with not decreasing the activity of the polymerization catalyst at the polymerization of propylene.