The invention provides a catalyst component for vinyl polymerization. The catalyst component is prepared by dissolving an organo-magnesium compound in a system containing an organic epoxy compound, an organosilicon compound and cyclodextrin or a derivative thereof in the presence of an inertial diluent so as to form a solution, then adding an acid halide compound and a titanium halide or derivative thereof and carrying out a reaction. The invention also provides a preparation method for the catalyst component and a vinyl polymerization catalyst based on the catalyst component. The catalyst component is simple to prepare, high in activity, polymer bulk density and melt index, and good in hydrogen sensitivity.