Abstract: Traditional wastewater treatment methods, such as physical, chemical and biological methods, still have many shortcomings in the treatment efficiency, human health and environmental protection, etc. However, the use of bio-nanocomposites can effectively solve the problems existing in the traditional wastewater treatment methods, which is a new material with great application prospects in wastewater treatment. This review described the synthesis mechanism of bio-nanocomposites, analyzed bio-nano composites for adsorption, photocatalytic and antibacterial mechanism of water treatment, and heavy metals in the water, organic dyes, drugs, inorganic salt and other contaminants removal applications, including hydroxyl groups on the surface of the material replaced by fluorine ion adsorption, chromium ions are adsorbed by electrostatic interaction and ion interaction. The biological part of the composite material can reduce the band gap and increase the adsorption area by absorbing the energy of a specific spectrum and catalyzing the oxidation of the pollutants adsorbed on the surface, which will eventually degrade or mineralize them. The material can directly interact with microbial cells to interrupt transmembrane electron transfer, destroy/penetrate cell envelope or oxidize cell components, or produce secondary products such as reactive oxygen species. The problems existing in controlling the morphology and particle size of nanoparticles, rapidly increasing the yield of nanoparticles and clarifying the toxicity of some sizes of nanoparticles were analyzed. In this paper the future development direction of bio-nanocomposites was put forward, achieving efficient control of green bio-nanocomposites production technology was expected. The next step is to focus on the precise mechanism of cellular and biochemical process, optimize the reaction parameters, improve the stability of the nanoparticles, explore the biological materials range of nano composite and form a mature synthesis technology scheme of bio-nanocomposites.