Abstract: The present invention relates to a method of preparing an ethylene polymerization catalyst, which comprises reacting a solid reaction product of magnesium halide (such as magnesium chloride), alcohol, an organic magnesium compound, and a halogen compound with a transition metal compound and an electron donor. When ethylene and a-olefin are co-polymerized by slurry polymerization in the presence of the above catalyst, the amount of wax component extracted by the polymerization solvent is very low, and the polymer particles do not agglomerate. The catalyst is prepared in the form of so uniform particles that the resultant polymer has uniform particle morphology, thus increasing bulk density.