The present invention relates to a primary catalyst, a preparation method and application thereof, and a catalyst composition containing the same. The primary catalyst comprises one or more of titanium compounds as catalyst activity centers with a general formula TiR1nX(4-n), one or more compound carriers containing magnesium, and an internal electron donor, which is added by a two-step addition method and comprises a) one or more aliphatic carboxylic acid esters and b) one or more aromatic dicarboxylic acid esters and / or diethers. During the polymerization process, the silane external electron donor is supplemented with aliphatic carboxylic acid ester, so that the catalyst gains more excellent performance. The catalyst provided by the invention has high catalyst activity and can be used for the preparation of a polymer with wide molecular weight distribution.