Abstract: Computational fluid dynamics(CFD) numerical simulation is employed on the middle tower caisson of Taizhou Bridge,analyzing its flow-force-induced vibration amplitude and cycle in different flow conditions.The vortex in the back of the caisson causes the vertical constant force and oscillation force and exciting force perpendicular to the flow direction.The volume of two kinds of forces decides the form of the vibration.A larger lift cycle amplitude change appears when 3.5×107≤Re<8.1×107.If the caisson is sinking in this Re scope,the anchor cable should be strengthened to prevent shimmy.