The proliferation of electromagnetic spectrum applications and increasing integration density of electronic devices have intensified electromagnetic pollution, driving demand for advanced electromagnetic interference (EMI) shielding materials. While conductive polymer composites present promising alternatives to traditional metals, attaining both exceptional EMI shielding performance and environmental sustainability remains challenging. Here, we adopt controlled mild alkaline hydrolysis to precisely engineer the surface roughness and hydrophilicity of polylactic acid (PLA) fibers, generating optimal substrates for subsequent electroless silver (Ag) deposition. The resulting Ag/PLA conductive fibers are structured into flexible films through vacuum filtration and hot-pressing. These films demonstrate remarkable electrical conductivity of 102,270 S/m, attributed to the continuous Ag coating and three-dimensional fibrous conductive network. Despite a thickness of merely 66 μm, the Ag/PLA films exhibit an ultra-high EMI shielding effectiveness (EMI SE) of 101.0 dB and a specific shielding effectiveness of 9749.4 dB·cm²/g. Notably, the films maintain military-grade EMI shielding performance (> 90 dB) after thermal cycling across a ~ 300 ^oC temperature range and 5000 bending cycles, confirming superior durability and mechanical flexibility. By synergistically coupling biodegradable PLA with recoverable Ag, this work simultaneously achieves outstanding EMI shielding performance and environmental sustainability, providing valuable insights for developing next-generation green EMI protection materials.