Widely applied in maintaining estuarial waterway depth,the spur dike has played an important role in currents and sediment exchange between channel and shoal and sediment back-silting in the channel.Through establishing a generalized physical model at a bifurcated estuary and conducting current tests under the joint action of runoff and tide,the influence of the spur dike length on current exchange between channel and shoal is analyzed.Results show that when the spur dike length reaches a certain value,the direction of the flow velocity shear front between the channel and shoal will change.The longer the spur dike,the larger the transverse fluctuating velocity at the peak of flood in the channel shoal exchange area,while the transport of the transverse hydrodynamics is obvious in the process of flood.There is an optimum length of spur dike when the shear stress in the channel and the longitudinal velocity in flood and ebb reach the maximum,and the flow velocity will decrease when the spur dike length is smaller or larger than the optimum.For a certain length of spur dike,the larger the channel shoal elevation difference,the larger the peak longitudinal flow velocity in the middle of the navigation channel in flood and ebb.However,the transverse flow velocity will first decrease and then increase.The transverse transportation is obvious when the channel shoal elevation difference increases. Widely applied in maintaining estuarial waterway depth, the spur dike has played an important role in currents and sediment exchange between channel and shoal and sediment back-silting in the channel. Establishment an generalized physical model at a bifurcated estuary and conducting current tests under the joint action of runoff and tide, the influence of the spur dike length on current exchange between channel and shoal is analyzed. Results show that when the spur dike length reaches a certain value, the direction of the flow velocity shear front between the channel and shoal will change.The longer the spur dike, the larger the transverse fluctuating velocity at the peak of flood in the channel shoal exchange area, while the transport of the transverse hydrodynamics is obvious in the process of flood. where is an optimum length of spur dike when the shear stress in the channel and the longitudinal velocity in flood and ebb reach the maximum, and the flow velocity will decrease when the s For di certain length of spur dike, the larger the channel shoal elevation difference, the larger the peak longitudinal flow velocity in the middle of the navigation channel in flood and ebb. However, the transverse flow velocity will first decrease and then increase. transverse transportation is obvious when the channel shoal elevation difference increases.