The invention relates to a method for improving emissivity of a paint film. The method comprises the following specific steps: (1) washing the surface of the paint film with an ion source while controlling the washing time to be 1min-10min; (2) plating a transparent emissivity regulating film on the surface of the paint film, wherein the plating is realized by performing sputtering deposition of the transparent emissivity regulating film on the surface of the paint film three times by adopting different sputtering rates. By adopting the method provided by the invention, a high-emissivity transparent film material is prepared on the surface of the paint film by the sputtering method, so that the paint film has high emissivity.