Olefin polymer and preparation method thereof

The invention relates to an olefin polymer and a preparation method thereof. The method comprises the following steps of contacting the olefin polymerization catalyst system with one or more olefin under olefin polymerization condition, wherein the olefin polymerization catalyst system comprises solid component, external electron donor compound and organo-aluminum compound, the solid component comprises titanium, magnesium and internal electron donor compound, and the external electron donor compound is diisopropyl dimethoxy silane and tetraethoxysilane. The olefin polymerization method not only has good hydrogen regulation sensibility, but also has high polymerization efficiency, and is especially suitable for preparing propene polymer through a vapor phase polymerization manner.