The present invention relates to a process for manufacturing polyolefin polymerization catalysts and provides a process for manufacturing polyolefin polymerization catalysts, wherein after manufacturing a homogeneous solution of magnesium compounds using magnesium compounds and alcohols along with hydrocarbon solvents and contacting with titanium compounds by adding organic aluminum, the mixture is treated again with organic aluminum or alcohols having 5 or less carbon atoms, then contacted with titanium compounds. Polyolefin polymerization catalysts prepared by the preparation process of the present invention have superior polyolefin polymerization activities, they prepare polymers having high Melt Flow Ratios, and produce a lesser amount of fine particle polymers.