N,O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes crosslinked by ECH were developed using a method of coating and crosslinking, where an epichlorohydrin/ethanol 96.7% (0.067 M KOH) solution was used as the crosslinking agent. The structure and the morphology of the resulting membrane were characterized by attenuated total reflection infrared spectroscopy (ATR-IR) and environmental scanning electron microscopy (ESEM). The effects of preparation conditions on the rejection performance of the resulting composite membrane were also investigated. At 20 degrees C and 0.40 MPa the rejections of the resulting membrane to Na2SO4 and NaCl solutions (1000 mg L-1) were 90.4% and 27.4%, respectively, and the permeate fluxes were 7.9, and 10.8 kg m(-2) h(-1), respectively. The rejections of this kind of NOCC/PSF composite NF membrane to the inorganic electrolyte solutions decreased in the order of Na2SO4, NaCl, MgSO4, and MgCl2.