A method for extracting residual DNA in edible vegetable oil is carried out by transferring DNA in oil and fat and enriching into aseptic water by water-emulsifying method, adding extracted buffer liquor with CTAB, Tris, NaCl and EDTA into water bath between 63-67 deg. C, keeping temperature for 30-60 mins to obtain aqueous extract, adding purifying agent with phenol, trichloromethane and isopropyl alcohol into aqueous extract, purifying, removing organic phase and aqueous phase to obtain purified liquor, adding precipitant into pre-cooled purified liquor, agitating, laying aside at -25--18 deg. C, precipitating while eluting DNA, separating, washing, and drying to obtain final product. It can be used to extract DNA from soya bean oil, corn oil, rapeseed oil and cottonseed coil. It has high-purity template DNA and need to purify.