In this research, novel asymmetric polysulfone (PSF) membranes were prepared from PSF/polyethylene glycol (PEG)/polyoxyethylene sorbitan monolaurate/1-methyl-2-pyrrolidone (NMP) system via immersion precipitation. Pure water was used as gelation media. The variation effect of coagulation bath temperature (CBT) and addition of surfactant on morphology, wettability, and pure water flux (PWF) of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measuring instrument, and experimental set up. The contact angle measurements demonstrated that hydrophilicity of the PSF membranes was significantly enhanced by small addition of surfactant in the casting solution along with using the lowest level of CBT. Also it was found out that addition of the surfactant in the casting solution along with increasing the CBT incites the formation of the bigger pores on the top surface and results in the formation of membranes with higher thickness and more porous structure in the sublayer. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers