Abstract: Utilizing the high strength and high strength - to - mass ratio of lignin - containing cellulose nanofibers (LCNF), the introduction of LCNF into polyvinyl alcohol (PVA) can enhance the mechanical properties of the composite film. LCNF was chosen as the reinforcing phase. After mixing cellulose nanofibers and lignin, the LCNF film was fabricated through vacuum filtration. PVA was physically cast at various concentrations and thicknesses to prepare LCNF/PVA composite film materials. Due to the hydrogen - bonding interaction between LCNF and PVA, the tensile strength of the composite film increased from 75.4 MPa to 142 MPa. Regarding the ultraviolet (UV) shielding issue of the composite film, lignin imparts excellent UV - shielding properties to the film. When the lignin content is 29.5 ± 2.31%, the shielding rates of the composite film for the ultraviolet A (UVA) and ultraviolet B (UVB) bands are 96.53% and 99.9%, respectively. The addition of LCNF enables the visible - light transmittance of the composite film to reach 78.4%, endowing the composite film with good gloss, transparency, and imaging performance. The LCNF/PVA composite film, owing to its high tensile strength and remarkable UV - shielding capabilities, has potential applications in food packaging, UV protection, and agricultural mulch films.