After the computation region of desilting filter of sediment of circular ring was especially treated, the paper chose some reasonable boundary conditions, used Volume of Fluid(VOF) method to trace free-surface and combined standard RNG model to simulate 3-D water flow field in the desilting filter of sediment of circular ring. Meanwhile,the vorticity field and velocity as well as the flow line of all the measured planes inside the equipment are all presented.The computed result has some instructive significance for the study of characteristic of flow field in the desilting filter of sediment of circular ring.