Abstract: Recently, under the joint influences of both human activities and natural factors, nutrient concentrations in the world coastal water is increasing year by year, which results in eutrophication and marine pollution to various levels. Often happened are red tide, fish death, shellfish poisoning, seaweed and seaweed bed disappearance, coral reef damage etc. It has caused great concerns from both governments and researchers. Based on the historical data and recent investigation, we studied in this paper the sources and characteristics of nutrients in Laizhou Bay of the Bohai Sea, assessed the current status and possible causes of eutrophication and discussed the impacts of eutrophication to the ecological environment thereby.