Poly (3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT:PSS) is a new conductive film material. In order to improve the physical properties of the film, an effective secondary doping method is adopted. The conductivity of PEDOT:PSS film was improved by secondary doping with various inorganic acids. The physical properties of doped film were tested and analyzed by four point probe method and UV spectrophotometer. Atomic force microscope (AFM) was used to measure the surface morphology of the film. The internal structure of the film was analyzed by X-ray photoelectron spectroscopy (XPS) and Hall effect testing system.