The invention relates to a method for preparing functional fatty, in particular to a preparing method of diacylglycerol. The preparing method comprises the steps that: (1) 50 shares of animal oil or vegetable oil in weight, 5-30 shares of water in weight and 0.03-0.20 shares of phosphatidase A1 in weight are mixed and reacted for 2 to 12 hours under the temperature of 30 to 70 DEG C and stand for1 to 2 hours or centrifugalize to delaminate; (2) the oil layer gained by delamination on the condition of temperature of 80 to 95 DEG C and absolute pressure of 4000 to 6000 Pa is dried for 30 to 60minutes to get crude diacylglycerol. Purified diacylglycerol can be gained through the elimination of free fatty acids under the temperature of 120 to 160 DEG C and absolute pressure of 0.1 to 40 Pa.Phosphatidase A1 used by the invention has fine catalysis effect and the price is only 5 percent to 10 percent of fatty acid enzyme which leads to significant decrease of cost and fine application prospect in industry.