The invention belongs to the technical field of electrolytic copper foil processing and particularly relates to a surface treatment composite additive capable of improving the corrosion resistance of copper foil. Every liter of the aqueous solution of the composite additive contains 1.0-10 g of polyethylene glycol, 0.1-5.0 g of rare-earth salt, 0.1-15 g of sodium dodecyl benzene sulfonate and 0.2-3.0 g of chitosan. The prepared composite additive is good in control performance and high in stability. The composite additive is used during galvanization, and thus the crystal morphology of a coating can be changed. The coating on the surface of the produced copper foil is smooth and uniform, crystals are fine and compact, the hydrochloric acid degradation resistant rate of the copper foil is lower than 3%, and good corrosion resistance is achieved. In addition, the production process is simple and environmentally friendly, the cost is low, waste foil obtained after surface treatment can also be recycled, and the index of the copper foil is not influenced.