Herein, we present a strategic approach to fabricate ultra-thin, structured electromagnetic interference (EMI) shielding films with Janus hydrophilic/hydrophobic surfaces, integrating polyetherimide (PEI) microsphere synthesis, silver (Ag) surface deposition, and solvent casting techniques. PEI microspheres with a diameter of ~ 4.78 μm are firstly synthesized via an emulsion technology. PEI@Ag composite films with a thickness of 25 ± 5 μm were fabricated by conformal deposition of a dense silver shell through chemical plating and subsequently a micro-oscillation casting method. These films synergize ultra-thin dimensions with exceptional EMI shielding performance, which corresponds to an exceptional SE-to-thickness ratio (SE/t) of 1.2 × 10³ dB/mm, thereby highlighting the pronounced benefit derived from its ultra-thin architecture. Beyond shielding performance, these films demonstrate outstanding thermal stability, acid/alkali corrosion resistance, and efficient Joule heating conversion, coupled with remarkable flexibility and lightweight characteristics, while retaining the unique Janus wettability. Such multifunctional integration renders the films highly attractive for advanced EMI shielding applications in extreme outdoor environments, highlighting their potential as next-generation solutions for demanding engineering scenarios.