Developing ultrathin and robust high-performance electromagnetic interference (EMI) shielding materials with multifunctional integration for wearable electronics is imperative yet remains challenging. Here, we report a bioinspired versatile and wearable MXene/cellulose nanofiber-silver nanowire (MXene/CNF-AgNW) composite film with superior mechanical strength, high-efficiency EMI shielding and integrated self-powered sensing capabilities. The film achieves superior mechanical robustness with a high tensile strength reaching 315 MPa through a multiscale reinforcement strategy that combines hybrid sandwich and nacre-like structures. The sandwiched AgNWs with MXene/CNF-based shells impart the composite film with high electrical conductivity and excellent EMI shielding effectiveness (EMI SE) reaching 62 dB for a tiny thickness of 23 μm, corresponding to an outstanding specific EMI SE (SSE/t) of 16550 dB·cm²·g^-1, together with remarkable electrothermal conversion capability. Furthermore, the flexible and antibacterial film can also serve as wearable electronic skin with self-powered sensing for human activity monitoring and information coding. Notably, by integrating a machine learning algorithm, the system can enable intelligent handwriting recognition with an accuracy of 100%, establishing an advanced communication interface. This work provides a facile multiscale engineering strategy for constructing multifunctional composite films that seamlessly integrate protection, perception, and communication functionalities for next-generation smart wearable electronic applications.