The present invention provides protectin (docosahexaenoic acid, DHA) from docosahexaenoic acid DX(Protectin DX), which is unsaturated fatty acid. DX(Protectin DX) Is an eco-friendly method which is not reported to date, and thus can be usefully used in various industrial fields such as, medicine DX foods and cosmetics, and the protectin, prepared according to the present invention is, human being used as DX a signal transfer substance . The. is expected to be involved in various bioactive functions in animals including animals.