Abstract: Oil-water separation is the main subject in many oil fields in the world. The mechanical behaviors and features of discrete phase droplet in oil-water emulsion are close related to separator efficiency. In this paper through the shear flow induced by rotation of two concentric barrels, the effect of shear stress on separation of oil-water emulsions was investigated experimentally. Some regulations of discrete droplet movement and agglomeration were discovered. Meanwhile, a criterion to estimate the effect of a shear flow on separation efficiency of emulsions by the distortions of droplet applied by the shear stress was proposed.This project provides not only a guide to the subsequent research on the mechanical behaviors and features of separated phase droplet in oil-water emulsion,but also a new way to develop oil-water separation facilities of high-efficiency.