Next-generation wearable electromagnetic interference (EMI) materials need to be provided with oxidation resistance, lightness, and flexibility. In this study, a high-performance EMI film with synergistic enhancement of Zn²⁺@Ti₃C₂T_x MXene/cellulose nanofibers (CNF) was found. The unique Zn@Ti₃C₂T_x MXene/CNF heterogeneous interface facilitates the loss of interface polarization, making the total electromagnetic shielding effectiveness (EMI SE_T) and shielding effectiveness per unit thickness (SE/d) of the films reach 60.3 dB and 5025 dB mm⁻¹, respectively, in the X-band at the thickness of 12 μm ± 2 μm, significantly exceeding that of other MXene-based shielding materials. In addition, the coefficient of absorption gradually increases with the increasing CNF content. Moreover, under the synergistic effect of Zn²⁺, the film shows excellent oxidation resistance (maintaining stable performance after 30 days), greatly exceeding the previous test cycle. Furthermore, the mechanical performance and flexibility of the film are greatly enhanced (tensile strength at 60 MPa, and maintaining stable performance after 100 times bending tests) due to the CNF and hot-pressing process. Therefore, with the enhancement of the EMI performance, high flexibility and oxidation resistance under high temperature and high humidity conditions, the as-prepared films have wide practical significance and broad application prospects in a series of complex applications, such as flexible wearable fields, ocean engineering fields and high-power device packaging fields.