The invention relates to the technical field of propylene and butylene copolymerization in petrochemical industry and discloses a preparation method of a propylene-butylene copolymer with high butylene content. The preparation method is performed according to the following steps: adding a required amount of cocatalyst, complex electron donor, Ziegler-Nalta catalyst precursor, butylene and liquid propylene into an oxygen-free and water-free polymerization reactor for carrying out a copolymerization reaction to obtain a copolymer; and drying the obtained copolymer to obtain the propylene-butylene copolymer with high butylene content. The propylene-butylene copolymer with high butylene content, prepared by using the preparation method of the propylene-butylene copolymer with high butylene content, contains more than 5wt% of butylene, is wide in molecular weight distribution, good in flowability and favorable in impact property and transparency and can be applied to the field of injectionmolding.