Jinmeng Bay （JMB） is one of the famous bathing beaches in the Bohai Bay. Green tides have occurred in JMB since 2015， which had a serious effect on aquaculture and tourism. Based on the MIKE 21 hydrodynamic and water quality model， the temporal and spatial distribution characteristics of the main pollutants in JMB were simulated and analyzed. A principal component analysis was conducted for assessing the water quality in JMB and its adjacent waters. The results show that the tidal current in JMB is mainly reciprocating flow along the shore， which is very weak. The current direction was southwest in flood tide and northeast in ebb tide. The variation of temporal and spatial distribution of water quality in JMB is significant. In temporal terms， the water pollution is more serious in the wet season than that the normal season and the dry season. In spatial terms， the pollution is more serious in the estuary than that in the offshore area and the water quality in the Tang estuary is obviously inferior to that in other estuaries. Finally， some suggestions were proposed which would provide reference for further prevention and control of pollution in JMB.