The invention relates to a preparation method of conjugated linoleic acid, and specifically relates to a preparation method of a composition containing at least 55 wt.% of conjugated linoleic acid, and the method is as follows: i) providing a liquid mixture containing at least 50 to 95 wt% of conjugated linoleic acid and at least 5 wt% of C12-C22 saturated fatty acid as a free acid; ii) cooling the liquid mixture to a certain temperature to precipitate at least a portion of the C12-C22 saturated fatty acid as a solid at the certain temperature; and iii) separating the solid from the liquid to obtain a liquid containing at least 55 wt.% of conjugated linoleic acid.