Abstract: Non-ionic surfactants were added into casting solution of polysulfone ul-trafiltration membrane as additives. Pure water fluxes and rejectiones to PEGs with differentmolecular weight of the membranes were measured.SEM pictures were taken for typicalmembranes. Comparing with the membrane without surfactant in it,the results did not showsignificant differnece on the support layers,but the skin layers of the membranes werechanged.The membrane pore size was bigger and pore size distribution was wider when thesurfactant added was hydrophilic. Contrarily,the membrane pore size was smaller and poresize distribution was narrower when the surfactant was hydrophobic,Studing the effect ofsurfactant in the process of membrane formed,surface tension and gelation speed of castingsolutiones were measured.The effect of surfactant was mainly changing the gelation speed ofthe casting solution. The gelation speed-time relation was obtained