Abstract: The Regional Ocean Modeling System (ROMS) is used in this paper to construct a three-dimensional dynamic model for the Qionghai coast. Based on hydrodynamic verification, the monthly variations of coastal marine dynamic process are simulated, and the response process of the marine dynamic structure to the seasonal wind fields studied. The study revealed the seasonal upwelling current along the Qionghai coast, and discussed the influence of the spatial marine dynamic structure on the erosional and depositional pattern of the coastal area. The results show that the Qionghai coastal ocean dynamic process has obvious seasonal features. It is strong in winter and summer, but weak in spring and autumn. In winter, the structure and direction of the surface and bottom flow fields are basically the same, but surface velocity is much higher than the bottom. In summer, however, due to the development of wind-induced upwelling, the surface flow field and the bottom flow field structure are significantly different. The wave-induced shear stress is relatively strong in the coastal area, and the current-induced shear stress is relatively strong on the north and south sides, making the Qionghai coast and the north and south sides of the coastal area a high-risk area vulnerable to erosion. The central and southeastern part of the study area, however, remain under deposition.