Abstract: Aramid nanofiber (ANF) is an ideal building block for fabricating high-strength composite materials because of its large aspect ratio, high specific area, a plenty of amide group on the surface, and excellent mechanical properties. In this work, a novel hydrogel processing strategy was developed to prepare ANF-reinforced poly(vinyl alcohol) (PVA) composite films. The loading of ANF, pre-stretching ratio of ANF/PVA hydrogel and chemical crosslinking of PVA component were optimized step by step. The dispersion and orientation of ANF, the crosslinking form of PVA, and the interfacial hydrogen bond between ANF and PVA were characterized and analyzed. It is confirmed that the mechanical properties reach maximum values when ANF loading, pre-stretching ratio and the used crosslinking agent are 25wt%, 55% and CuCl₂, respectively. The Young’s modulus and tensile strength of the resultant composite film are as high as (14.6±0.3) GPa and (496.5±10.0) MPa, far superior to previously reported ANF-reinforced polymer composites. Moreover, the high-strength composite film has good transparency and excellent UV light shielding property. Its transmittance is larger than 72.1%, while it can shield more than 99.98% UV light. We believe that the transparent yet UV light-blocking composite film can be applied as advanced packaging materials.