Doped polyaniline films were prepared with electrochemistry method. A small conjugated molecule, anthracenecarboxylic acid(2-ACA), was used as the dopant, considering its electrical activeness due to the conjugated π-π* structure. Film morphology of doped and undoped polyaniline samples was investigated. The corresponding changes in optical and electrical properties after ACA doping were discussed. By measuring and calculating their energy level distribution, a promising application of polyaniline thin films as buffer layer in optic-electric devices is expectable. A small conjugated molecule, anthracenecarboxylic acid (2-ACA), was used as the dopant, considering its electrical activeness due to the conjugated π-π * structure. Film morphology of doped and undoped polyaniline samples was investigated. The corresponding changes in optical and electrical properties after ACA doping were discussed. By measuring and calculating their energy level distribution, a promising application of polyaniline thin films as buffer layer in optic-electric devices is expectable.