After construction of water conservancy in the navigable river，the discharge of the unsteady water flow which is similar to the man-made flood peak and clear water of near to zero sediment concentration from the peaking power generation destroys the balance of the river，and thus brings a new topics for research on bed evolution and waterway regulation technology.Based on the flume experiment and theory analysis，we study the starting and transport rule of uniform sediment under the action of unsteady flow in the hub’s downstream. The result reveals that changing process of sediment rate under unsteady flow and flow condition are not synchronized,and it relates to the intensity of the unsteady flow P.When P is larger than 032,the sediment peak generally lags behind the rate of flow parameters of the peak;when P is less than 032,the sediment discharge peak may occur before the peak flow parameters.