Abstract: Polyaniline-polyimide-polyaniline (PANI-PI-PANI) compound film was prepared through an insitu growth on PI film matrix in dispersion polymerization. The processing and driving force of PANI film deposited on PI matrix were studied by processing tracing of reaction, SEM and static drop contact angleinterfacial tension tester. Results show that the process of PANI film deposited on PI matrix takes on three obvious stages. First, constitutional units containing aniline segment, such as An hydrochloride, An cation free radical, and oligomer, are adsorbed onto PI matrix and nucleates. Second, film quickly grows. Third, growth completes. PANI film is formed with a gradual accumulation of small grains of polyaniline, until the entire surface of PI film is covered. The main driving force of PANI film is the hydrophilichydrophobic interaction.