The invention provides a bactericidal scale and corrosion inhibitor for seawater desalination, and belongs to the technical field of chemical engineering. The bactericidal scale and corrosion inhibitor comprises, by weight, 10-15% of polyquaternary ammonium salt, 20-30% of sodium polyepoxysuccinate, 20-30% of polyaspartic acid-polymaleic anhydride, 5-10% of a zinc salt, 5-10% of dodecyl dimethyl benzyl ammonium bromide, and the balance of water. The bactericidal scale and corrosion inhibitor has scale inhibition, corrosion inhibition and sterilization functions, and all components of the bactericidal scale and corrosion inhibitor have very good intermiscibility, cooperativity and complementarity, so the bactericidal scale and corrosion inhibitor can substitute present single function scale and corrosion inhibitors and bactericides, and has comprehensive functions; and a formula and a preparation method of the bactericidal scale and corrosion inhibitor are green, compound raw materials adopted in the invention contain no phosphorus and cause no water eutrophication, discharged water causes no pollution to environment, and the preparation method is simple and feasible, is a clean technology, and has no emission of industrial three wastes.