Based on the bed evolution analysis and river model test,we study the hydro-dynamic characteristics of Shuangjian shoal beach protection engineering in Fujiang shoal reach.Analyses of riverbed evolution indicate that Shuangjian shoal is located in the reach with multi-level branches,the body of Shuangjian shoal is often scoured and deposited,the head of Shuangjian shoal moves forward and backward frequently,which are both the key factors influencing the steadiness of the channel condition and the change of scour and silting in each branch.Through the analyses of tide level,velocity and diversion ratio,etc.,the protecting effect of the “herringbone” shaped protection engineering recommended by the preliminary research,the influence on the river regime,flood control,and surrounding areas are all studied.The results show that,after implementing the beach protection engineering,the beach ditch is blocked off,and the beach flow is decreased,Shuangjian shoal and the pattern of the swale are stabilized gradually,which can improve the channel condition and lay a foundation for the 12.5 m deepwater channel selection and regulation.