Propene polymer and preparation method thereof

The invention relates to a preparation method of a propene polymer, comprising the following step of polymerizing propene and a mixture of the propene and ethylene and/or alpha-olefin in a reactor in the existence of a catalyst under the condition of olefin polymerization to obtain the propene polymer, wherein the catalyst contains a solid component, an alkylaluminum compound and an external electron donor compound, the solid component contains an internal electron donor compound, the internal electron donor compound contains an internal electron donor compound a and an internal electron donor compound b, the internal electron donor compound a is a diol ester compound shown as a general formula I, and the internal electron donor compound b is one or more of unitary aliphatic carboxylic ester, polybasic aliphatic carboxylic ester, unitary aromatic carboxylic ester except for the diol ester compound shown as the general formula I, polybasic aromatic carboxylic ester and a 1,3-dietheric compound. The propene polymer provided by the invention not only has higher isotactic index and molecular weight, but also has a wider molecular weight distribution range.