In this article, the effect of co-solvent (N-methyl-2-pyrrolidone (NMP)/diethylene glycol dimethyl ether (DGDE)) of the dope solution on the morphology, mechanical property and the pervaporation performance of the polysulfone (PSf) hollow fiber membranes prepared via a wet spinning process were investigated.. Water was employed as the external coagulant, 70 wt.% NMP in water was used as bore liquid. The rate of solvent-nonsolvent exchanged during membrane formation was characterized by Fourier transform infrared (FT-IR) microscopy. The addition of DGDE in the dope solution decreases the exchange rate of solvent-nonsolvent during the membrane formation process, resulting in the suppression of the macrovoids formation. The tensile stress, elongation at break and Young's modulus of the PSf hollow fiber membranes increased with increasing the DGDE content. In addition, the effects of DGDE content, feed composition and feed solution temperature on the pervaporation performances were also investigated. The permeation rate and separation factor towards water for a 90 wt.% aqueous ethanol solution through the asymmetric PSf hollow fiber membrane with a NMP/DGDE (8/2) ratio of co-solvent system were 172.7 g/m(2) h and 23.9, respectively.