The invention relates to a soil fertilizer technique, in particular to a long-acting slow-release corn special blending fertilizer and a preparation method thereof to solve the problems that the nitrogen and phosphorus utilization rate of the fertilizer is low, the after manuring in the corn growth period consumes a large amount of time and labor and the like. The blending fertilizer comprises the following components in percentage by weight: 45 to 58 percent of nitrogen fertilizer, 16 to 25 percent of phosphate fertilizer, 16 to 25 percent of potassium fertilizer, and 4 to 14 percent of nitrogen phosphorus fertilizer synergist; and nutritive substances of the blending fertilizer comprise the following components in percentage by weight: 24 to 28 percent of pure nitrogen, 8 to 12 percent of diphosphorus pentanitride, and 10 to 15 percent of potassium oxide. The preparation method comprises the following steps: adding the granular nitrogen fertilizer, phosphate fertilizer, potassium fertilizer and the nitrogen phosphorus fertilizer synergist into a mixing and stirring machine according to the weight ratio, mixing and stirring the materials evenly to obtain the long-acting slow-release corn special blending fertilizer, and performing sub-package to obtain the finished product; or selecting a urease inhibitor, a nitrification inhibitor and a phosphate fertilizer synergist to granulate by mixing so as to obtain the granular nitrogen phosphorus fertilizer synergist, and then blending the granular nitrogen phosphorus fertilizer synergist with the granular nitrogen fertilizer, phosphate fertilizer and potassium fertilizer to obtain the finished product. The long-acting slow-release corn special blending fertilizer and the preparation method have simple process and easy implementation, are suitable for one-step basal application without after manuring for corn production in the Northeast, and reduce the usage amount by 10 to 20 percent without reducing the yield.