NOVELTY - Preparing Dendrobium fertilizer involves adding phosphoric acid, heating at 90-130 degrees C, mixing carboxamide, reacting for 180-200 minutes, centrifuging the mixture to obtain intermediate, passing ammonia gas into the reaction vessel containing intermediate, fermenting for 40-60 minutes, circulating the mixture through cooling chamber, crystallizing cooled mixture, drying the crystals to obtain ammonium dihydrogen phosphate, adding potassium in the prepared crystals and drying prepared mixture, until the moisture content reaches 3-4% to obtain the product.    USE - The method is useful for preparing Dendrobium fertilizer (claimed).    ADVANTAGE - The method enables to prepare nutritious Dendrobium fertilizer, and is cost-effective.    DETAILED DESCRIPTION - Method for preparing Dendrobium fertilizer involves (a) adding phosphoric acid in the reaction vessel, heating at 90-130 degrees C, then adding carboxamide to obtain carbamide phosphate, reacting for 180-200 minutes, cooling to 15-30 degrees C and centrifuging the mixture to obtain a intermediate, where the molar ratio of phosphoric acid and carboxamide is 1.2-1.4:1, (b) passing ammonia gas into the reaction vessel containing intermediate, fermenting for 40-60 minutes, adjusting pH to 8.5-9.5, circulating the mixture through cooling chamber, crystallizing cooled mixture, simultaneously determining the nitrogen and phosphorus contents of the crystals, terminating crystallization, when the mass ratio of nitrogen and phosphorus in the crystal reaches (1.8-2.2):(0.8-1.2), and drying the crystals to obtain ammonium dihydrogen phosphate, where the molar ratio of ammonia and intermediate is (1.1-1.3):1, and (c) adding potassium compound in the prepared crystals, adjusting the potassium, nitrogen and phosphorus contents to 4-6 %mass, 9-11 %mass and 4-6 %mass, respectively, adding micronutrients, drying prepared mixture by increasing temperature to 25-35 degrees C at a rate of 3 degrees C/minute, until the moisture content reaches 3-4% to obtain the product.