The technology of heavy oil transportation by core-annular flow is attracting more and more attention.In the process of transporting high-viscosity crude oil in the water film, it will inevitably pass through the elbow pipe and other components.Under the effect of centrifugal force in the elbow, the core oil flow is close to the wall surface, and it is easy to lose stability.In this paper, the FLUENT software is used to study the numerical simulation of the oil water annular flow in the 90 degree elbow by using the VOF model.Its stability characteristics are studied through comparison of different interfacial tensions.The results show that the interfacial tension has a significant effect on the stability of the core annular flow in the elbow.Under the simulated conditions, the interfacial tension increases to 0.25N/m, which is the best for the stability of the core annular flow through the elbow.