Lignin, a biomass-derived material containing chromophores, possesses the potential to serve as a versatile organic ultraviolet (UV) light screening agent. By employing quantum chemical computation techniques, an amphoteric deep eutectic solvent (DES) based on sulfamic acid was purposefully designed and engineered to create a solvent system tailored for the nanoparticle formation and functionalization of lignin. As confirmed by experimental evidence, the size of the modified lignin nanoparticles (LNPs) varies from 168.4 to 388.8 nm, with molecular weights ranging from 1806 to 2093 g/mol, and a PDI of 1.51 to 1.67. The nano-processing of lignin, along with auxochrome addition, induced a shift in the absorption peak to a longer wavelength spectrum, from 359 to 379 nm. Furthermore, the results confirmed a significant increase in absorption, particularly within the UVA radiation band, for lignin treated in this system. Quantum chemical calculations verified that incorporating a G-type structure with a β-5 bond significantly enhanced lignin's UV absorption in the UVA spectrum, and the presence of auxochrome shifted its absorption peak to longer wavelengths.