The present invention relates to a small pore size catalyst component for olefin polymerization or copolymerization, and a preparation method thereof. According to the present invention, a magnesium halide is dissolved in an organic epoxy compound, an organic phosphorus compound and an inert diluent and a silane compound can further be added to form a uniform solution, the obtained uniform solution and a titanium halide or a titanium derivative are subjected to a reaction in the presence of a co-precipitating agent, a particle shape improving agent is added before the magnesium/titanium-containing solid precipitate is precipitated, an electron donor is loaded or is not loaded on the solid precipitate after the solid precipitate is formed, and washing is performed with an inert diluents so as to obtain the product; the small pore size catalyst component has characteristics of smooth particle surface, less cracks and an average pore size of less than or equal to 2 nm; when the small pore size catalyst component is used for propylene polymerization and copolymerization, the fine powder content in the powder material is low; and the small pore size catalyst component is suitable for slurry methods, bulk methods, gas phase methods, and other polymerization processes.