The present invention discloses a double-effect water-protecting fertiliser and a preparation method thereof, wherein per 1000kg finished product of the double-effect water-protecting fertilizer is composed of the following components by weight: 40.0 to 80.0kg of biochemistry fulvic acid, 225.0 to 265.0kg of carbamide, 60.0 to 100.0kg of calcium ammonium nitrate, 200.0 to 250.0kg of mammonium dihydrogen phosphate, 80.0 to 120.0kg of magnesium kalium sulphuricum, 135.0 to 175.0kg of kalium sulphuricum, 0.5 to 3.5kg of borax, 2.0 to 6.0kg of copper sulfate, 10.0 to 18.0kg of zinc sulfate, 5.0 to 15.0kg of toluol methylpyrrolidine, 10.0 to 40.0kg of crosslinked polypropylene acidamide and polyacrylic acid potassium salt copolymer, and 10 to 40kg of attapulgite powder clay. the fertiliser not only meets the food supply required by the health growth of farm crops, is also capable of improving the utilization efficiency of the soil moisture and having non harm to human and animal husbandry without environment pollution.