Thermal annealing treatment on polysulfone supporting (PS) layer was adopted to develop nanofiltration (NF) membranes with high thermal stability and high ion selectivity. The structure and properties of the resulted PS and NF membranes were systematically characterized by atomic force microscopy (AFM), a scanning electron microscope (SEM), attenuated total reflectance infrared (ATR-IR) spectroscopy, a drop shape analysis system and an electrokinetic analyzer. The structure relationship between PS skin layer and NF active layer was verified according to the results from AFM and SEM analysis. Furthermore, thermal stability of NE membranes was evaluated under a wide range of temperature and pressure. Cycling temperature impact was applied to Lest the recoverability and stability of salt rejection of NF membranes. Through simulating the practical operation conditions, ion selectivity of NF membranes to monovalent and multivalent ions was further investigated using standard 1812 elements. It was verified that thermal annealing treatment has great effects on the microstructure of both PS layer and NF active layer. NE membranes with annealed PS layer showed strong thermal durability and high ion selectivity. (C) 2014 Elsevier B.V. All rights reserved.