The invention relates to the technical field of guitar strings, in particular to a double-coating nanometer string with an anti-fouling, rust-proof and anti-aging function. The string comprises a hexagonal steel core, the outer wall of the hexagonal steel core is spirally wound with a metal wire, the outer wall of the metal wire is covered with a nanometer wear-resistant layer, and a nanometer anti-fouling layer is sprayed on the outer wall of the nanometer wear-resistant layer; the metal wire is a steel wire, copper wire, nickel wire or silver wire, the number of the metal wire is one, and the metal wire is any one of the steel wire, the copper wire, the nickel wire or the silver wire and is wound on the outer wall of the hexagonal steel core; the number of the metal wires is two, and thetwo metal wires are any one combination of two of the steel wire, the copper wire, the nickel wire and the silver wire and are wound on the outer wall of the hexagonal steel core in a stacked mode; and the number of the metal wires is three, the three metal wires are any three metal wires of the steel wire, the copper wire, the nickel wire and the silver wire and are wound on the outer wall of the hexagonal steel core in a stacked mode. The string has good anti-fouling, rust-proof and anti-aging performance compared with the existing strings.