Flat sheet asymmetric PSf/clay nanocomposite membranes with different clay dosage were prepared by phase inversion method. Dimethyl acetamide was used as a solvent and water was used as a coagulant. PEG 400 was used as a pore forming additive in the casting solution. The morphology and structure of membranes were analyzed by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The performance of membranes was evaluated in terms of pure water flux (PWF), protein rejection, porosity, contact angle, tensile strength and elongation at break respectively. Results showed that clay had a good dispersion in the PSf matrix. The addition of clay additive increased the ratio of large pore in the skin layer and weakened the tensile strength. PWF and porosity of membranes increased with the increase of clay dosage. With increase in clay dosage from 0 wt.% to 6 wt.%, the PWF increased from 342 L m(-2) h 1 to 382 L m(-2) h(-1). (C) 2011 Elsevier B.V. All rights reserved.