The invention relates to double enzymes, which are characterized by comprising double enzymes and serial fertilizers of urea, a compound fertilizer (a mixed fertilizer), a bulk blending fertilizer, diammonium phosphate, monoammonium phosphate, a nitrophosphate fertilizer and a nitric phosphate-potassium fertilizer, wherein in terms of the total weight of the double enzymes, the content of the double enzymes is 0.01-15wt%, and the total content of the urea, the compound fertilizer (the mixed fertilizer), the bulk blending fertilizer, the diammonium phosphate, the monoammonium phosphate, the nitrophosphate fertilizer and the nitric phosphate-potassium fertilizer is 99.99-85wt%; and the double enzymes are prepared by mixing a main enzyme, namely metalloprotease, with an auxiliary enzyme according to the proportion of (1-30%):(1-35%). The invention also relates to a preparation method of a double-enzyme serial fertilizer, which comprises the steps of: directly and uniformly mixing the double enzymes with molten serial fertilizer slurry or a powdery serial fertilizer, or uniformly adding the double enzymes into the serial fertilizer materials after the processing of a drying device in the production process of the double enzymes; and other processes for the serial fertilizers, such as powdery or granular double-urea, a double-enzyme compound fertilizer (mixed fertilizer), a double-enzyme bulk blending fertilizer, double-enzyme diammonium phosphate, double-enzyme monoammonium phosphate, a double-enzyme nitrophosphate fertilizer, and a double-enzyme nitric phosphate-potassium fertilizer, are similar the production process of the serial fertilizers. Besides, the invention also relates to the application of the double-enzyme serial fertilizers to field crops, economic crops, fruits and vegetables and flowers in the agriculture.