The work aims to develop electromagnetic shielding material that is both highly efficient in its shielding capabilities, lightweight, and offers good thermal stability. In this study, PPy/PI electromagnetic shielding composite films were fabricated using the electrostatic spinning-low temperature in-situ polymerization technique with polyimide (PI) as the polymer matrix and polypyrrole (PPy) as the reinforced phase. By establishing a dense conductive network within the film's porous structure, the composite film exhibited excellent electrical conductivity and efficient electromagnetic shielding effectiveness. The conductivity and electromagnetic shielding effectiveness of the composite film were 2.23 S/cm and 26.04 dB when the PPy of.1 mol/L was polymerized, and the effectiveness of its electromagnetic shielding per unit thickness could reach 110.81 dB/mm, which was a remarkable performance for electromagnetic shielding. Additionally, the PPy/PI composite fiber film has excellent mechanical properties (with a tensile strength of 11.73 MPa), excellent thermal stability (>400°C) and mechanical sensing properties, with the potential to have a variety of uses in harsh environments.