The utility model discloses an anti-corrosion device for a pile foundation in a salt marsh area, which comprises a steel pile casing, the steel pile casing is a variable-diameter combined steel pile casing, the variable-diameter combined steel pile casing comprises a large-diameter steel pile casing and an ordinary steel pile casing, and both ends of the large-diameter steel pile casing and both ends of the ordinary steel pile casing are open; The outer diameter of the large-diameter steel casing is larger than that of an ordinary steel casing, and the inner diameter of the large-diameter steel casing is equal to that of the ordinary steel casing. The large-diameter steel casing is composed of a first inner casing wall, a first outer casing wall and steel trusses, the first inner casing wall and the first outer casing wall are coaxially sleeved, and the first inner casing wall and the first outer casing wall are connected through the multiple sets of steel trusses. Concrete is poured between the first inner cylinder wall and the first outer cylinder wall; According to the anti-corrosion device disclosed by the utility model, the two steel casings with different diameters are combined together, so that the corrosion resistance of the reinforced concrete pile at different depths in a salt marsh area is increased, and the purpose of saving materials can be achieved.