A solid titanium complex catalyst for polymerization and copolymerization of ethylene is prepared by the process that includes: (1) preparing a magnesium solution by reacting a halogenated magnesium compound with an alcohol; (2) reacting the magnesium solution with an ester compound having at least one hydroxyl group and a silicon compound having an alkoxy group to produce a magnesium composition; and (3) producing a solid titanium catalyst by reacting the magnesium composition solution with a mixture of a titanium compound and a haloalkane compound; and optionally reacting the solid titanium catalyst with an additional titanium compound.