A numerical model which contains wave,tidal flow and sediment is established and the model is verified by wave,tidal current,sediment and siltation changes of topography,to solve the problem of the depth reserved for sedimentation under synchronous construction of breakwater and waterway at a port area of Dongying port.On the basis of the mathematical model,the construction process is decomposed into several nodes for modeling and calculation,and the statistics of different time stages from the end of construction to completion acceptance are combined.We gain the rule of waterway siltation during the period of synchronous construction and prediction the depth reserved for sedimentation.The above studied achievements can not only provide a technical support for the waterway channel project,but also offer positive basis for reference for similar study.