Abstract: The present invention relates to a method for preparing a high activity olefin polymerization catalyst, which is easy to be produced, reducing complicated steps, and can be produced at low temperature, wherein said method comprising the following steps: • (a) adding a magnesium halide into an alcohol solvent; • (b) precipitating the solution obtained from (a) in a solution of an organic solvent containing an organo compound of group III element; • (c) adding a titanium compound into the mixture obtained from (b) to obtain a catalyst; • (d) treating the catalyst obtained from (c) with an organoaluminium compound at a temperature ranging from 0 to 60° C. for 2 to 5 hours, wherein the mole ratio of aluminium to titanium (Al/Ti) for treatment is in a range of 1 to 30.