Abstract: A series of polytetrafluoethylene-polyaniline(PTFE-PANI) conductive composite films synthesized by electrochemical method were heat-treated in air or vacuum atmosphere. The conductivity and mechanical properties in different atmospheres were studied by thermogravimetric(TG) analysis, infrared ray(FT-IR) and X-ray diffraction (XRD). TG results showed that the residual of mass of the composite film was minor from 100 °C to 180 °C. The conductivity of PTFE-PANI composite film dropped at the heat treatment temperature region in air and vacuum，so did the PTFE-PANI-Ag composite film in air. The mechanical strength of the series of composite films changed less, while the elongation at break reduced dramatically. The conductivity of PTFE-PANI-Ag composite film got a maximum in vacuum at 120 °C, and its mechanical strength improved while the elongation at break reduced. XRD spectra results showed that the crystallinity of PTFE-PANI film was lower after heat treatment at 180 °C in air. FT-IR spectra results showed that 5-sulfosalicylic acid dedoped from PTFE-PANI composite film, and benzene rings transformed into quinone by thermal oxidation. At the same time, thermal oxidation also caused break and cross-linking of the PANI molecule chain, therefore the conductivity of the films decreased.