Oil droplets in nanometer scale which are dispersed in water cannot be separated easily. An attractive technique is carried out by electrical phenomena to demulsify oil in water emulsion. In this research, non-uniform electric field or dielectrophoresis (DEP) is applied to remove sunflower oil (which is dispersed in the water). Effects of temperature, time and voltage (using AC-electric field) were considered to get the highest DEP-force (F-di) and the best results. The oil particles sizes with average of approximately 76 nm have been shown using a ZetaSizer Nano ZS, Model ZEN 1600 (Malvern Instrument Ltd.). The maximum separation efficiency of 85% is obtained at the optimum temperature of 38 degrees C and voltage of 3000 V.