Abstract: The water exchange time distribution of the Pulandian bay is firstly modeled, and then the effectiveness of the present pollutant outlets layout is evaluated basing on the water exchange time distribution, water quality criterion of the marine functional zoning and water quality distribution obtained during the extensive observations in spring 2015.The water exchange time distribution calculated with the Lagrangian passive particles tracking method provided by ROMS shows that the water exchange time of the Pulandian bay varies greatly in different regions depending on the changing bathymetry and twisting coastline.In the western open areas, the water exchange capacity is strong with an average water exchange time less than 20 days while in the semi-enclosed eastern areas, especially the middle part and eastern reach of the bay, the water exchange capacity is extremely weak with the average water exchange time longer than 300 days.The anti-clockwise eddy-shaped circulation in the central part of the bay blocks the pollutants transports from the inner part of the bay to the outer part.The outlets with heavy pollutants discharges are all located in the areas with weak water exchange capacity.The water exchange time of the pollutants is much longer than the time the pollutants desire in order to exert influence on the local marine ecosystem.The accumulation of the pollutants leads to a deterioration of the water quality.The water quality distribution obtained during the extensive observations indicates that the water quality in the middle part and eastern reach of the bay is much worse than the according water quality criterion of the marine functional zoning.A more environment friendly pollutants outlets layout will be a prerequisite when a better water quality in the Pulandian bay could be expected.