A hydrophilic bamboo cellulose nanofiltration membrane (IP-NF-BCM) was prepared through interfacial polymerization (IP) of amino-functional piperazine (PIP) and 1,3,5-trimesoyl chloride (TMC) on a cellulose surface. The in situ formation of polyamide into the mesoporous structure of the regenerated cellulose film created a uniform microporous membrane, which can be used for water softening by nanofiltration. The interfacial polymerization reaction conditions were optimized in terms of the performance of resultant nanofiltration membranes. The chemical structure, morphology, and surface charge of the composite membranes were characterized based on thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), nuclear magnetic resonance (NMR), and Brunauer?Emmett?Teller (BET) nitrogen absorption. The water permeation and salt rejection capability of the bamboo cellulose thin-film-composite nanofiltration membranes were evaluated using 500 ppm salt solutions at 0.5 MPa pressure. Results show that the rejection rate for NaCl reached 40% and water flux reached 15.64 L/(m2·h). The average pore size of the bamboo cellulose thin-film-composite membranes was 1.0 nm.