The present invention relates to a method for treating a metal surface, comprising (A) providing an ionic liquid solution and a substrate of a first metal, wherein the ionic liquid solution comprises an ionic liquid and an ion of a second metal; and (B) immersing the substrate of the first metal in the ionic liquid solution to form a coating layer of the second metal on a surface of the substrate of the first metal by reducing the ion of the second metal. The surface of the substrate of the first metal is protected by the coating layer of the second metal, thereby improving the corrosion resistance.