The present invention provides an ethylene polymerization catalyst. The present invention also provides a process for preparing the ethylene polymerization catalyst, comprising reacting powdered magnesium with an alkyl halide of formula RX in the presence of an ether solvent to form a magnesium compound having a structure represented by the formula (RMgX).sub.p(MgX.sub.2).sub.q, in which R is an alkyl group having from 3 to 12 carbon atoms, X is halogen, and molar ratio of q to p is in the range of from larger than 0 to 1, impregnating the magnesium compound onto silica carrier, reacting the silica loading the magnesium compound with an alkyl halide of formula R.sup.1X, a titatium compound and an alkyl aluminum compound to form a main catalyst component, contacting the main catalyst component with a cocatalyst component to form catalyst for ethylene polymerization. The present invention also relates to the use of the catalyst in the polymerization of ethylene.