Abstract: Rapid urbanization and human activities have led to a significant increase of nutrient concentration in coastal waters following critical eutrophication problem. It is the prerequisite for effective coastal management to understand the relationship between nutrient dynamic and land-based pollution. Based on the water quality monitoring data of Xiamen Bay in Fujian Province from 2010 to 2019, this paper studied seasonal and long-term spatial distribution of water quality, evaluated the eutrophication status of Xiamen Bay with Eutrophication Index Method and provided suggestions for the nutrient pollution remediation. The results showed that the concentration of DIN and DIP gradually decreased since 2013 while DIP concentration in Tongan Bay increased rapidly in recent years. DIN and DIP concentrations in spring and winter were apparently higher than those in summer. The concentrations decreased seaward with increasing salinity, reflecting typical characteristics of terrestrial nutrient input. NO₃-N was the main component of DIN and its ratio to DIP was generally higher than the Redfield ratio. Controlled by river input and sewages discharge, both DIN and DIP were the main factors brought high eutrophication indexes to the Jiulong River Estuary, Western Xiamen Bay and Tongan Bay. Besides, DIP was likely affected by the urban sewage in autumn. Xiamen Bay is urgently needed to control the nitrogen and phosphorus disposals focusing the surrounding river watersheds and urban sewage.