The invention provides an antioxidant of baking food and a preparation method thereof. The antioxidant includes 55-60 parts by weight of hydrogenized soya bean lecithin, 10-18 parts by weight of vitamin E, 5-10 parts by weight of soyabean protein polypeptide, 2-3 parts by weight of oligo-xylose, 1-5 parts by weight of sucrose monostearate, 2-3 parts by weight of xanthan gum and 11-20 parts by weight of baked milk powder. The preparation method includes extracting lecithin from the soya bean lecithin, separating catalyst, discoloring oxydol, removing solvent after the reaction of catalytic hydrogenation, obtaining hydrogenized soya bean lecithin with 20-30 of iodine number, uniform mixing 55-60 parts by weight of hydrogenized soya bean lecithin, 10-18 parts by weight of vitamin E, 5-10 parts by weight of soyabean protein polypeptide, 2-3 parts by weight of oligo-xylose, 1-5 parts by weight of sucrose monostearate, 2-3 parts by weight of xanthan gum and 11-20 parts by weight of baking milk powder to prepare the antioxidant for baking food. The invention has the advantages of strong antioxygenic property, pure natural property, no toxic and side effects, a plurality of healthcare functions.