Poly (N,N-dimethylaminoethyl methacrylate)/polysulfone (PDMAEMA/PSF) positively charged nanofiltration (NF) membrane was developed by the interfacial crosslinking polymerization using PSF flat-sheet microfiltration (MF) membrane as support layer, PDMAEMA aqueous solution as coating solution, p-xylylene dichloride/n-heptane as crosslinking agent. This membrane has a rejection to inorganic salts in aqueous solution. The rejection of MgSO4 (1 g/L aqueous solution) is almost 90% and the rejection of NaCl (1 g/L aqueous solution) is almost 78% at 0.8 MPa and 30degreesC. The rejection of the following inorganic salts to this membrane is decreasing in the order of MgCl2, MgSO4, NaCl and Na2SO4. The membrane exhibits higher permeate flux and rejection of inorganic salts in a neutral solution than in an acid or alkali solution. The membrane has a certain resistance to oxidative media or free chlorine. The results of the study also show that this membrane should be preserved in antiseptic solution. (C) 2004 Elsevier B.V. All rights reserved.