Dye pollution has become one of the main pollution sources in the world, and the water pollution caused by it needs people's close attention. Nanocellulose is a sustainable biomaterial that is abundant in nature and has many advantages, such as high crystallinity, high hydrophilicity, high Young's modulus, high strength, and high surface activity. Its surface has abundant hydroxyl functional groups, making nanocellulose and its composites well used in adsorbing dyes from wastewater. In this paper, the adsorption mechanism and adsorption process of nanocellulose and its derived materials on cationic dyes and anionic dyes were discussed comprehensively. The specific adsorption mechanism was summarized, including adsorption isotherm model, adsorption kinetics process, adsorption thermodynamics process, etc. In addition, this article also looks forward to the future development of nanocellulose and related materials in the field of water treatment, and proposes new development directions.