Multi-walled carbon nanotubes (MWNTs) functionalized by isocyanate and isophthaloyl chloride groups were synthesized via the reaction between carboxylated carbon nanotubes and 5-isocyanato-isophthaloyl chloride (ICIC). Furthermore, blends of polysulfone (PSF) and functionalized MWNTs with different composition dissolved in dimethylformamide (DMF) were used to prepare ultrafiltration membranes by a classical phase-inversion method. It was found that the content of functionalized MWNTs was an important factor influencing the morphology and permeation properties of the blend membranes. The pure water flux of the blend membranes increased with the content of functionalized MWNTs, up to 0.19%, and then gradually decreased. The static water contact angle of the blend membrane surface showed that the hydrophilicity of the surface increased with the content of functionalized MWNTs; in the blend. In addition, SEM images of the blend membrane surface and cross-section showed that the average pore size and pore structure of the blend membranes changed with the content of functionalized MWNTs up to 0.19%, and after that, the average pore size decreased. Finally, protein adsorption performance of membrane indicated that MWNT content suppressed the adsorption of protein on membrane, and thus alleviated membrane fouling. (c) 2009 Elsevier B.V. All rights reserved.