The Kouanzhi 12.5 meter-deep-water channel regulation project is located in the left branch of the Yangzhong River and the main construction work consists of ripraps.The project area is characterized by long distance offshore,deep water depth,changing flow velocity range,etc.It is difficult to accurately predict the riprap throwing point at the construction site.Thus we carry out a field experiment for riprap throwing distance,and obtain a formula for predicting the throwing distance at the period of the rising and falling tide,which is further used in Manyu-Shoal submerged-dike construction.The results show that the riprap throwing distance is influenced by the tidal current acceleration,which becomes larger during current velocity increasing period while smaller during current velocity decreasing period.Overall,when the current acceleration is smaller than 1.5×10-3m/s2,the throwing distance prediction formula coefficient can be taken as a uniform value of 0.892 for the whole tidal process. When the throwing distance of the group’s median riprap is smaller than 4.5 m,the averaged throwing distance of riprap group can be estimated by proposed formula with a median diameter of the group chosen.The measured dike section profile agrees well with the designed one.This work provides a good method for accurate throwing distance prediction in tidal river.