A method for constructing a hydrophilic antifouling coating on a surface of a medical implantable material, comprising the following steps: 1) pretreating a surface of a medical implantable material to obtain a clean surface and/or a hydrophilic active site; 2) impregnating the medical implantable material that has been pretreated in step 1) in a precursor solution for a reaction so as to obtain a free radical reaction and/or polymerization site on the surface of the medical implantable material; and taking out the medical implantable material for later use; 3) performing a polymerization grafting reaction after obtaining the free radical reaction and/or polymerization site on the surface of the medical implantable material in step 2), placing the medical implantable material in a reaction solution for the polymerization grafting reaction, wherein the reaction solution comprises a crosslinking agent, the modified molecules and an initiator; and 4) after the reaction in step 3) is completed, performing washing and drying, thus finishing construction of a hydrophilic antifouling coating on the surface of the medical implantable material, wherein in step 3), a mass percentage concentration of the modified molecules is 0.1-50%; a mass percentage concentration of the crosslinking agent is 0.001-50%; a reaction temperature is 10-100°C; and a reaction time lasts for 1-10 h; in step 3), the crosslinking agent is selected from an alternating-structure amino acid copolymer; the structural formula of the alternating-structure amino acid copolymer is as follows: abbreviated as n, wherein A is B is n is an integer; and n=2-10000: R 1 comprises, but is not limited to, the following structures: -CH 2 -CH 2 -CH 2 -NH 2, - CH 2 -CH 2 -NH 2, -CH 2 -CH 2 -CH 2 -CH 2 -NH 2, and -CH 2 -CH 2 -NH-CNH-NH 2; R 2 comprises, but is not limited to, the following structures: -H, -CH 2 -CH=CH 2, -CH 2 -CH 2 -CH=CH 2, C 6 H 5 -CH 2 -, and -CH 3 -C 6 H 4 -O-CH 3; and R 3 comprises, but is not limited to, the following structures: -H, -CH 3, -CH 2 -CH 3, -CH 2 -CH 2 -CH 3, -CH-(CH 3) 2, -CH 2 -COOH, -C(CH 3) 3, and -CH 2 -C 6 H 5; in step 3), the modified molecules are a hydrophilic substance or a mixture of the hydrophilic substance and a hydrophobic substance; the hydrophilic substance is one or more of acrylates, zwitterionic substances, polyethylene glycol substances with different molecular weights, or polyvinylpyrrolidone; the acrylates comprise one or more of 2-hydroxyethyl methacrylate, 2-ethoxyethyl acrylate, and poly(ethylene glycol) methyl ether methacrylate; the zwitterionic substances comprise one or more of 2-methacryloyloxyethyl phosphorylcholine, carboxybetaine, and sulfobetaine; and the hydrophobic substance comprises one or more of lauryl methacrylate, vinyltrimethylsilane, tert-butyl methacrylate, and cyclohexyl methacrylate. 1) pretreating a surface of a medical implantable material to obtain a clean surface and/or a hydrophilic active site; 2) impregnating the medical implantable material that has been pretreated in step 1) in a precursor solution for a reaction so as to obtain a free radical reaction and/or polymerization site on the surface of the medical implantable material; and taking out the medical implantable material for later use; 3) performing a polymerization grafting reaction after obtaining the free radical reaction and/or polymerization site on the surface of the medical implantable material in step 2), placing the medical implantable material in a reaction solution for the polymerization grafting reaction, wherein the reaction solution comprises a crosslinking agent, the modified molecules and an initiator; and 4) after the reaction in step 3) is completed, performing washing and drying, thus finishing construction of a hydrophilic antifouling coating on the surface of the medical implantable material, wherein in step 3), a mass percentage concentration of the modified molecules is 0.1-50%; a mass percentage concentration of the crosslinking agent is 0.001-50%; a reaction temperature is 10-100°C; and a reaction time lasts for 1-10 h; in step 3), the crosslinking agent is selected from an alternating-structure amino acid copolymer; the structural formula of the alternating-structure amino acid copolymer is as follows: abbreviated as n, wherein A is B is n is an integer; and n=2-10000: R 1 comprises, but is not limited to, the following structures: -CH 2 -CH 2 -CH 2 -NH 2, - CH 2 -CH 2 -NH 2, -CH 2 -CH 2 -CH 2 -CH 2 -NH 2, and -CH 2 -CH 2 -NH-CNH-NH 2; R 2 comprises, but is not limited to, the following structures: -H, -CH 2 -CH=CH 2, -CH 2 -CH 2 -CH=CH 2, C 6 H 5 -CH 2 -, and -CH 3 -C 6 H 4 -O-CH 3; and R 3 comprises, but is not limited to, the following structures: -H, -CH 3, -CH 2 -CH 3, -CH 2 -CH 2 -CH 3, -CH-(CH 3) 2, -CH 2 -COOH, -C(CH 3) 3, and -CH 2 -C 6 H 5; in step 3), the modified molecules are a hydrophilic substance or a mixture of the hydrophilic substance and a hydrophobic substance; the hydrophilic substance is one or more of acrylates, zwitterionic substances, polyethylene glycol substances with different molecular weights, or polyvinylpyrrolidone; the acrylates comprise one or more of 2-hydroxyethyl methacrylate, 2-ethoxyethyl acrylate, and poly(ethylene glycol) methyl ether methacrylate; the zwitterionic substances comprise one or more of 2-methacryloyloxyethyl phosphorylcholine, carboxybetaine, and sulfobetaine; and the hydrophobic substance comprises one or more of lauryl methacrylate, vinyltrimethylsilane, tert-butyl methacrylate, and cyclohexyl methacrylate.