A large volume of wastewater in the form of oil-in-water (o/w) emulsions is generated from various industries such as petrochemical, food, traortation, and oil refineries. There are several techniques to remove oil form water. Typical ones include physical, chemical and biological methods. There are some advantages and disadvantages for each of these techniques. Membrane separations have been developed greatly over the last 30 years and are becoming a promising technology. They have high oil removal efficiency, low energy consumption and compact design compared with traditional treatment method. Many studies on membrane separation for oily wastewater treatment have been reported, particularly in microfiltration (MF), and ultrafiltration (UF) with polymeric and membranes. These studies mainly were focused on fouling and methods to enhance flux or mitigate fouling. In this research coagulation-flocculation process incorporated with membrane separation as a new approach for oily wastewater treatment. The coagulation has been done in two ways, before membrane and during membrane filtration (inline coagulation). The first objective of this study was to investigate the efficacy of pre-coagulation or inline coagulation on oil removal and performance of UF process. The second aim of the project was to optimize operating conditions during coagulation and filtration. Optimization performed for three coagulants (alum, poly aluminum chloride (PAC), and chitosan) in jar and in filtration equipment. Central composite design (CCD) and response surface methodology (RSM) were applied to optimize the two most important operating variables: coagulant dosage and pH in coagulation. In filtration set up the effects of trans membrane pressure, cross flow velocity and type of membrane were studied on permeate flux, turbidity and COD removal. It is shown that increasing of trans membrane pressure and cross flow velocity increases steady permeate flux. It was observed that turbidity and COD removal efficiency decreases with increasing of trans membrane pressure and cross flow velocity. The reason is that oil permeation from oil layer on the surface of membrane is higher at higher pressure. At higher flow velocity due to higher shear rate oil drops break in smaller drops which are more permeable through the membrane. It was observed that higher oil concentration decreases flux while removal efficiency is not affected significantly by oil concentration. It also observed that coagulation and settling before UF has better results than inline coagulation. The reason may be that floc has more time to enlarge. In combined process (coagulaton+filtration) of oily water contains 0.5% v/v of oil poly aluminum chloride had higher efficiency than aluminum sulfate. For this concentration at the optimum conditions, the removal of turbidity and COD were 92% and 89%, respectively. When coagulant added to the feed of UF process permeate flux, turbidity and COD removal were 51 l/m 2 h, 79%, and 77%, respectively. For wastewater containing 1% v/v, using chitosan and poly aluminum chloride for pre- treatment step leads to turbidity and COD removal of 95% and 87%, respectively. Statistical results demonstrate that all of proposed models possess high confidence limit, and permeate flux of 41 l/m 2 h , turbidity removal of 79% and COD elimination of 79% have been obtained at optimum conditions. Key Words: oily wastewater, ultrafiltration, coagulation, optimization.