A significant portion of the world's crude oil is produced in the form of oil-water emulsions. The effective separation of oil and water dispersions could be considered as one of the critical steps in determination of the economic and technical success of the petroleum industry for many years. Deep understanding of basic droplet coalescence at the interface and different parameters that are effecting on this phenomenon is essential for characterization of the global phase separation.An experimental investigation of the coalescence of single droplet at the interface of Exxsol-aqueous phase was carried, with emphasis on the effect of aqueous phase composition and droplet size on stability of droplets. A Coalescence Time Measurement (CTM) facility is utilized to measure mean coalescence time at the liquid-liquid interface and examine how it could be affected by droplet size, viscosity of the continuous phase and the composition of aqueous phase, which is crucial for characterization of the global separation process.Moreover statistical analysis of CTM data is conducted to develop relationship among the coalescence time and process controllable variables (droplet size, continuous phase viscosity, interfacial tension, density of dispersed phase and continuous phase, salinity and hydrate inhibitor concentration).