<p>Lignin, an abundant and renewable natural aromatic polymer, faces a major obstacle in its high-value utilization due to its dark color. To address this limitation and enable its application in light-colored polymer materials, this study developed a mild and efficient chemical reduction decolorization method. Sodium borohydride (NaBH₄) was employed as a reducing agent to selectively target chromophoric groups, such as carbonyl C=O, within the lignin macromolecule. Fourier transform infrared spectroscopy (FT-IR) confirmed a significant reduction in C=O groups and a concurrent increase in hydroxyl content following modification. The decolorized lignin was subsequently compounded with cellulose nanofibrils (CNF) to successfully fabricate high-performance composite films. Compared to films containing unmodified lignin, the modified lignin-based composite films exhibited substantially lighter coloration alongside enhanced comprehensive properties, including markedly improved toughness (elongation at break), excellent UV-shielding capability, enhanced flame retardancy, good biodegradability, and effective preservation functionality for blueberries. This study provides a simple and effective strategy for lignin decolorization and its application in the field of green packaging.</p> Graphical Abstract <p></p>