The invention relates to a method for preparing an antioxidative active extractive of sweet potato leaves, and belonging to the field of agriculture products processing. The method comprises the following steps: drying and crushing fresh sweet potato leaves; performing microwave assistant extraction after the decoloring and degreasing treatment is carried out; decompressing and concentrating extract in vacuum; chromatographing through a column, and absorbing by maroporous resin; collecting eluent; decompressing and concentrating the eluent in vacuum to obtain extract of the sweet potato leaves; and atomizing and drying the extract to obtain powdered extractive of the sweet potato leaves. The product is powdered, has the unique smell of the sweet potato leaves, contains 65 to 75 percent oftotal phenol, and contains chlorogenic acid and 3,5-O-dicaffeoylquinic acid. The method adopts mass waste sweet potato leaves to prepare the extractive with strong antioxidative activity, turns wasteinto wealth, is a green industry, has simple process, no need of larger equipment investment and high extracting rate of antioxidative active substances, and is applicable to industrial production.