Abstract: Gas-liquid stratified flow in a horizontal pipe is one of the important research subjects of pipe transportation and horizontal well oil extraction. A foremost concern is the interface of gas-liquid, especially the stratified flow with bubbles passing through the interface. It is an inescapable and challenging problem in horizontal well oil extraction with wall injection. In this paper, gas-liquid interface is captured by means of VOF(Volume of fluid), and 3-D unsteady Reynolds-averaged Navier-Stokes equations are solved by using FVM (Finite volume method) and RNG κ-ε turbulence model. The typical stratified flow field with mass exchange through interface, interface shape and resistance at interface are obtained.