We discussed in this paper the transportation of sediment in the water around the Haiyang Harbor, and predicted the evolution of the sandy coast after the construction of the East Wing of the Haiyang Harbor, using the hydrodynamic and sediment transportation numerical model and based on various data including hydrology, meteorology, water depth, and surface sediments. The impacts of the construction of the East Wing of the Haiyang Harbor on the erosion and deposition system of the surrounding waters were unraveled. The results revealed that sediments in the study area are generally moving in a trend from west to east. The erosion and deposition in the waters between the east and west wings will be weakened after the construction of east wing, but enhanced in the south and north. The sandy coast will suffer from siltation after the construction and reach a dynamic balance within a time span of 5 years.