Abstract: The study on the problem of flow around circular cylinder is significance for study of seabed messenger pipes. In the action of drag, lift and the coupling between seabed and soil, phenomena such as displacement and spanning have great threat for the safe running of submarine pipelines. Correct prediction of the force between pipe and flow under various flow conditions is the most important task to ensure the safety of oil and gas pipeline. The interaction between large diameter pipeline and flow in extreme sea environment might cause high Reynolds number flows problem. Flow simulation at high Reynolds numbers are more complicated than that at low Reynolds. For flow simulation, it is necessary to use more fine mesh and suitable turbulence model. In this article, submarine pipeline in suspended has been simulated, and the flow field structure under different clearance ratio has been discussed. In addition, the influence of the clearance ratio on flow drag and flow lift has been analyzed, providing with load boundary data for further study of stress and deformation of free spanning submarine.