A novel positively charged composite nanofiltration (NF) membrane was prepared using 2-hydroxypropyltrimethyl ammonium chloride chitosan as active layer, polyacrylonitrile ultrafiltration membrane as substrate layer, and 1,4-butanediol diglycidyl ether as cross-linking reagent. The observation from scanning electron microscope revealed its composite structure. At room temperature and cross-flow rate of 40 L h(-1), the permeability for pure water was 14.3 L h(-1) m(-2) MPa-1. With an increase in operating pressure, the flux increased linearly. The rejection to different salt solutions was decreasing in the order of CaCl2, MgCl2, MgSO4, NaCl, and Na2SO4, revealing the rejection characteristic of positively charge NF membrane. And it had good ion perm-selectivity. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2358-2364, 2010