A provided humic-acid-containing modified-starch-coated slow-release fertilizer comprises the following compositions in parts by weight: 75-85 parts of urea, 2-5 parts of potassium superphosphate, 1-3 parts of sodium hydroxide, 3-9 parts of N,N'-methylenebisacrylamide, 1-5 parts of ammonium sulfate, 2-6 parts of ammonium chloride, 1-4 parts of potassium dihydrogen phosphate, 2-6 parts of deionized water, 2-8 parts of microcrystalline wax, 1-5 parts of collophane powder, 2-8 parts of sodium alginate, 6-12 parts of modified starch, 3-9 parts of cellulose derivative, 1-3 parts of humic acid, 2-6 parts of acrylic acid, 3-8 parts of copper potassium pyrophosphate, and 2-6 parts of ammonium polyacrylate. According to the technical scheme, the nutrient release rate of the coated slow-release fertilizer is alleviated, the water retention capability of soil is improved, also the coated slow-release fertilizer is degradable, low in cost, and suitable for large-scale popularization and usage.