Bien Dong (Vietnam East Sea) is located in the most atmosphere-ocean active regions: Asian-Australian monsoon region and west Pacific warm pool, therefore the strong variability of weather, climate and extreme events are related with the regional and global air-sea-Iand interaction processes. In the condition increasing requirements on providing the information for management and exploitation of marine environment and resources, it is urgent to develop and establish a modeling system for marine environmental prediction and monitoring. After 10 years experiences in research and development, the system of the MDEC-VNU models had heen applied to simulate the three-dimensional thermohaline and circulation structure of the Bien Dong. This system was applied also to simulate the hydrodynamics, suspended matter and environmental components included oil in the Gulf of Tonkin and coastal estuarine areas as (Quang Ninh, Hai Phong, etc. The simulated results can help to explain as well the oil pollution case appeared in the Vietnamese coastalduring winter season 2007 as variation of water turbidity in the Do Son beach.