Polyethyleneimine/2-hydroxypropyl trimethyl ammonium chloride chitosan/TiO2 nanoparticles/trimesoyl chloride (PEI/HACC/TiO2/TMC) positively charged composite nanofiltration (NF) membrane using polysulfone ultrafiltration membrane as support layer and TiO2 nanoparticles as modifying agent was prepared by interfacial polymerization reaction. The separation performance of the NF membrane was tested by pure water, PEG1000 solution, salt solutions, dye solutions and mixed solutions of dye and salt. The membrane structure was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At the optimal preparation conditions of 3 wt.% PEI, 0.3 wt.% HACC, 0.9 wt.% TiO2, 1.5 wt.% TMC, reaction temperature of 20 degrees C and reaction time of 60 s, the NF membrane shows the high flux, the high dye rejection and the low salt rejection, which are suitable to the process of purifying raw dye. (C) 2012 Elsevier B.V. All rights reserved.