Abstract: Flexible pipelines in the ocean are severely impacted by the outside world. Different impactors will lead to different changes in the structure of the pipeline inner channel. In order to explore the influence of channel structure on annular flow structure, N-S equation and turbulence model were used to describe the flow. VoF model and CSF model were used to track the oil-water interface. Evolutions of turbulent kinetic energy, eddy structure, annular flow pattern and pressure field of the oil-water annular flow in the pipe were analyzed with different forms of structural deformation, different degrees of deformation and different flow velocities. The results show that the strength and the area of the vortex become larger with the increase of the structural deformation. The influence of V-shaped deformation is much greater than that of O-shaped deformation. When the flow pattern of annular flow changes, the stable state of oil phase wrapped by water phase is still maintained, and the oil-water interface pressure in the maximum compression region increases with the increase of speed. The conclusions obtained have certain guiding significance for studying the stability of oil-water annular flow in flexible pipeline transportation.