Abstract: The water in-crude oil emulsion has great importance in the oil industry. Experimental data are presented to investigate the stability of water-in-crude oil emulsions in both creaming and coalescence states were measured as a function of sodium chloride concentration. Also the stability of w/o emulsion is investigated over a wide range of parameters. These parameters are salt concentration (0-5.5%), mixing speed (800-1600 rpm), water concentration (10-80%) and temperature. For economic and operational reasons, it is necessary to separate the water completely from the crude oils before transporting or refining them. The emulsions were found to fall into three categories on the basis of both rheological properties and visual appearance: stable; mesostable and unstable. The present research found that, microwave radiation method can enhance the demulsification of water-in-crude oil emulsions in a very short time compared to the conventional methods.