There are many sluices built in tidal estuary, Zhejiang province, in which an important problem is scour protection for soft foundation of sluice downstream. By the study of hydraulic model test and prototype observation, the results show that to select natural sediment with the similarity law of strarting velocity to simulate the soft foundation of sluice downstream can reflect the practical condition, and that it is necessary to adopt the movable－ bed model for a project, which easy occurs fluival process caused by eroding. This results can be used for reference to analogous engineering.