A novel positively charged composite NF membrane was prepared using a copolymer graft of trimethylallyl ammonium chloride onto chitosan (GCTACC) as the top selective layer, a poly(acrylonitrile (PAN) ultrafiltration membrane as the support layer and toluene diisocyanate (TDI) as the cross-linking reagent. The effects of membrane preparation conditions on membrane performance were investigated such as TDI concentration, GCTACC concentration, etc. The observation from scanning electron microscopy suggested the composite structure of the resultant NF membrane. At 20 and 30 L.h(-1) of cycling flow, the permeability of pure water was 14.1 kg.h(-1). m(-2).MPa-1. The order of rejection to different salt solutions was MgCl2 > MgSO4 > NaCl > Na2SO4, revealing the characteristic of positively charged NF membranes.