Using high-intensity electric fields is a well-known technology in water emulsion improvement in petroleum. Its utilization is developing to improve the processes of crude oil in the form of water separation from hydrophilic impurities. Despite of numerous researches, there are some unknown aspects of field of electrostatic separation processes yet. In the separation method by the electric field, neutral particle that had been charged by the electric field, moves to higher intensity. The effect of this field is controlled by the dielectric constant of continuous and discrete environment. In this thesis, after reviewing the processes and applications of water emulsion in petroleum, the governing equations will be expressed. In this study, in order to create a non-uniform electric field, a two co-axial cylindrical glassy container and a graphite electrode (with very low electrical resistance) had been used. The experimental tests and numerical simulations for 5 and 10 percent water emulsion under non-uniform and DC electric field with 11,000 and 17,000 volts will be done. The experimental tests is to pour the water and edible oil emulsion in the inner layer and 98% sulfuric acid in the outer walls. Then the electrode is placed in inner and outer layer and the voltage is applied for 300 seconds. Then, for 30 seconds the voltage is removed and it is permitted to the water droplets to settle in the edible oil. Experimental results show that the best separation of water for water in edible oil emulsion that containing 10% water, with DC electric field and 17,000 volts is 62.5 percent. Numerical simulations of this process had been done by the mixture model which its formulation is a single fluid model. The electrical force is generated by an external force to the mixture model. The mixture model and electrical current modulus is pre-modified in COMSOL Multiphysics 5.1 software. By choosing this modulus and setting the boundary and initial conditions as happens in experimental test, the problem will be solved. In numerical simulations, the best separation of water from edible oil for water in edible oil emulsion that containing 10 percent water, under field of DC electric and 17,000 volts is 50 percent. By comparing experimental results and the results of numerical simulations after 330 seconds, it can be observed that occurring error is 15 percent. This error can be caused by considering the constant diameter for water droplets and considering the accumulation phenomenon instead of coalescence. In the experimental and numerical testing in this problem, voltage variations effects and electrical permittivity coefficient could be observed and according to obtained results it could be concluded that by increasing the voltage and water percentage in water and edible oil emulsion, the separation rate will improve. This happens when increasing the voltage and water percentage in emulsion, will not results in electrical refraction or chaining the water droplets. Key words: emulation of water from edible oil, non-uniform and DC electrical field, Euler model and mixture model, numerical simulation, test