In this study the removal of water from oil-in-water emulsion by ultrafiltration (UF) membrane was investigated at 40 degrees C and 3 bar in laboratory and pilot scale. Hydrophilic polyethersulfone (PES), polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) membranes were used to conduct laboratory tests. The effects of membrane material, nominal molecular weight cut off (MWCO), operating conditions and feed oil concentration in emulsion on UF behavior were studied. For PAN, PVDF membranes their permeate fluxes are much higher than that of PES membrane. The experimental results show that membranes with either high or low MWCO have high separation efficiencies. The PAN membrane has a prominent permeate ability at lower feed oil concentration (0.5 vol. %) compared with those of other UF membranes under same MWCO. PES membrane is suitable to remove water of higher feed oil concentration (5 vol. %) Comparing the pilot and laboratory results, similar oil and COD rejection are measured, while the permeate flux in pilot is significantly lower.