The key to make an ideal thin film composite membrane is the reduction of active layer thickness as much as possible to improve the water permeability without adverse effect on selectivity. Hence, ultra-thin nano-composite membranes were prepared via dip coating method composed of chitosan incorporated graphene oxide on the surface of polyethersulfone (PES) substrate, followed by ionic crosslinking with sodium tripolyphosphate (TPP). By incorporation of graphene oxide on the chitosan solution, the thickness of selective layer considerably decreased to around 45 nm and higher surface hydrophilicity was obtained. The chitosan/graphene oxide ultrathin modified nanocomposite membrane exhibited state-of-art flux (around 55 LMH) and high manganese removal (around 85%) at low pressure of 3 bar. Moreover, these membranes demonstrated up to 98% inhibition in the bacteria proliferation, indicating reasonable antibacterial activity of ultra-thin layer. Besides, the antifouling ability of the nanocomposite membrane increased dramatically, where the flux recovery ratio of 52% and 93% attained for BSA and E. coli, respectively.