Abstract: Atrovirens viscous liquid PAA/PANI-TiO2 was prepared by in-situ polymerization and ultrasonic oscillation method with 4, 4-two amino two phenyl ether (ODA) and pyromelliticdianhydride (PDMA) as the monomer, the PANI-TiO2 as the dopant, and then PI/PANI-TiO2 composite films were prepared by thermal imidization method. The structure, morphology and properties of the polyimide composite films were measured by means of FT-IR, SEM, TG-DTG, dielectric constant meter，and universal mechanical testing machine compared with PI film. The results showed that the thermal imidization of PI/PANI-TiO2 composite films was completely and the PANI-TiO2 particles were evenly distributed in the PI matrix. The tensile strength of PI/PANI-TiO2 composite films were increased from 14.8 MPa to 43.8 MPa with the addition of 10% mass fraction PANI-TiO2 particles, the initial degradation temperature was increased from 435℃ to 518℃ compared with pure PI, relative dielectric constant was increased from 3.38 to 3.86, dielectric loss factor was increased from 0.0013 to 0.0040. As a result the mechanical properties and thermal stability of PI/PANI-TiO2 composite films were enhanced compared with pure PI, the relative dielectric constant and dielectric loss factor were also increased.