Protective coating and preparation method therefor

A protective coating, comprising a first coating formed on a surface of a substrate by plasma polymerization deposition when the substrate contacts plasmas, and the plasmas comprise a plasma of a monomer A and a plasma of a monomer B, wherein the monomer A comprises a silicon structural unit of formula (I) and at least one amine group structural unit of formula (II) or formula (III), and the monomer B comprises a terminal carboxyl group structural unit

• wherein the plasmas also comprise a plasma of a monomer C, and the monomer C comprises one or more selected from a group consisting of a fluorohydrocarbon, a fluoroacrylate and a fluorosilane;
• or
• wherein the protective coating further comprises:
• a second coating on the first coating, the second coating comprises one or more layers of plasma polymerization coatings, and monomers of each layer of the second coating are respectively independently one or more selected from a group consisting of a fluorohydrocarbon, a fluoroacrylate and a fluorosilane.