Abstract：The flow around circular cylinders always is a problem of focus in ocean engineering, as related with platforms and oil pipelines. In this paper, the Fluent software is used to simulate the flow around multi-circular-cylinders, for several typical arrangements of multi-circular- cylinders. The simulation is based on the RANS equation and RNG turbulence model. It is shown that the flow around serial arrangements of two circular cylinders is related to the distance between the two cylinders. There is a symmetric and inverted vortex in the flow around two circular cylinders of the parallel arrangement. The flow around two circular cylinders of the staggered arrangement is similar to the flow around three cylinders of triangle-shaped arrangement or inverted triangle-shaped arrangement, and the fore circular cylinders restrain the vortex separation by the back circular cylinders. The vortex in the flow around four circular cylinders of square arrangement is unsymmetrical. The simulation results indicate that the simulation of multi-circular-cylinders viscous flow field using Fluent is effective, and the details of the flow around multi-circular-cylinders can be qualitatively simulated.