PPESK is of particular interest in the fabrication of OF membrane for its considerable mechanical strength, thermal stability and chemical resistance. However, its use in aqueous phase is restricted due to its hydrophobicity. NaA zeolite is one of most hydrophilic inorganic material with low atom ratio of Si:AI (1:1) and big channel diameter and good comprehensive performance which may have the potential to improve the properties of PPESK. Composite ultrafiltration (UF) membranes with entrapped NaA zeolite particles were prepared from poly(phthalazinone ether sulfone ketone) (PPESK). The membranes were prepared with phase inversion process and were characterized by OF experiments and scanning electron microscope (SEM) observations. At 3 wt.% NaA content, the composite membranes held excellent water permeability, hydrophilicity and good antifouling ability with enhanced retentions. Higher NaA content (than 3 wt.%) caused a particle aggregation to some extent according to the cross-section and external surface morphology. However, the excess incorporation of the zeolite particles did not cause decline of membrane performance according to the OF experiments. Antifouling performance was tested with resistance-in-series Model and flux decline in Titan Yellow dye solution. Thermal analysis (DSC) was performed in order to investigate the interactions between NaA particles and PPESK. PPESK OF membranes with different molecular weight cut-off (MWCO) and high flux were obtained by adjusting the polymer concentration. It was concluded that the membrane prepared in our laboratory had better performance than two kinds of commercial OF membranes. (C) 2009 Elsevier B.V. All rights reserved.