The invention provides a catalyst component for ethylene polymerization; the catalyst component is prepared by the steps: in the presence of an inert diluent, dissolving an organic magnesium compound in a system containing an organic epoxy compound, an organosilicon compound and cyclodextrin or a derivative thereof to form a solution, then acting on halide of titanium or a derivative thereof, to obtain a solid, and treating the solid with an organic aluminum compound to obtain the catalyst component. The invention also provides a preparation method of the catalyst component, and an ethylene polymerization catalyst based on the catalyst component. The preparation method of the catalyst component is simple, the catalyst activity is maintained at a high level, the polymer bulk density is high, the melt index is high, and the hydrogen sensitivity is good.