The invention discloses an oil field scale inhibitor including a first scale inhibitor, a second scale inhibitor and a third scale inhibitor, wherein the first scale inhibitor includes: 8-10 parts ofsodium ethylenediamine tetramethylene phosphonate, 5-8 parts of aminotrimethylenephosphonic acid, 3-5 parts of hydroxyethylidene diphosphonic acid, and 5-8 parts of 2-phosphonobutane-1,2,4-tricarboxylic acid; the second scale inhibitor includes: 15-20 parts of maleic anhydride, 5-10 parts of acrylic acid, 5-8 parts of hydroxypropyl acrylate, and 0.5-1 part of ammonium persulfate; the third scale inhibitor includes: 10-12 parts of polyepoxysuccinic acid, 8-10 parts of polyaspartic acid, 5-8 parts of modified imidazolines, 0.5-1 part of modified quaternary ammonium salts, and 0.05-0.1 parts of sodium polyacrylate. The oil field scale inhibitor has stable properties; when being injected into an oil well, the scale inhibitor is slowly released, thus effectively relieving scaling on the wall cylinder and prolonging pump inspection period. The invention also provides a preparation method and a use method of the oil field scale inhibitor.