Abstract: Polymeric mixed ionic-electronic conductors (PMIECs) can effectively conduct and couple ions and electrons, they play key roles in the development of the next-generation flexible bioelectronic, optoelectronic conversion and energy storage devices. This research fabricated a ionic-electronic hybrid film by in-situ polymerization of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) on Perfluorosulfonic acid membrane-Nafion. We characterized the properties of the film with scanning electron microscopy (SEM), electromechanical measurements, and stability tests in water. The results indicated that PEDOT: PSS layer was tightly attached to the Nafion film in the hybrid film, which helped to improve the stability of the device. Considering the time of polymerization may influence the uniformity of the conducting polymer electrode, thus may deteriorate the mechanical performance of the device and reduce the conductivity of the electrode. We investigated the relationship between the time of polymerization and conductive performance. Finally, we utilized this film to fabricate a sensor, and studied its electromechanical conversion performance and stability in different environments under different modes, which illustrated the potential application of this stable ion-electron hybrid film in emerging flexible and wearable electronic applications for human-computer interaction.