Silver nanorods/polyimide (Ag-NRs/PI) nanocomposites with high conductivity (An order of magnitude higher than pure PI), frequency-independent dielectric permittivity (3.8-4.2) and low dielectric loss (<0.05) were prepared by an in-situ polymerization process. Ag-nanorods with a mean width of approximately 300 nm and an average length over 8 microm were synthesized in the presence of polyvinylpyrrolidone (PVP) and NaCl by polyol process. SEM images showed that metallic Ag-nanorods were well dispersed in PI matrix. The structure of Ag-NRs was not destroyed or changed in nanocomposite films and the order of PI molecular chains was maintained as well. The orientation of the Ag-NRs in the PI matrix improved the mechanical properties of nanocomposite films. TGA results showed that the thermal property of nanocomposite films was almost as good as pure PI.