Abstract: Nutrients are essential elements for phytoplankton growth and also are the main pollution elements in China’s coastal waters. Based on the investigation of Hangzhou Bay and its adjacent sea in September of 2021, the structure and distribution characteristics of nutrients, the potential pollution sources of seawater were explored. According to the results, the average concentration of total nitrogen (TN) was 1153 μg/L and the main components of nitrogen were NO₃-N and dissolved organic nitrogen (DON) with the proportions of 40.9% and 39.1%, respectively. The average concentration of total phosphorus (TP) was 112 μg/L and the main components of phosphorus was particulate phosphorus (PP) with the proportion of 61.7%. Nutrients spatial distribution of surface water showed that the concentrations decreased gradually from nearshore to offshore, and nutrients distributions of bottom layer in Shengsi area were significantly different with surface layer. The vast majority of N/P ratios (except PN/PP) were generally greater than 16 indicating P-limited. Concentrations of NO₃-N, dissolved inorganic nitrogen (DIN), DTN and TN were positively correlated with salinity (correlation coefficient were 0.757, 0.736, 0.693 and 0.710) which indicated their behaviors were conservative, and the concentrations were mainly controlled by the mixing with seawater. Correlation coefficients of NH₄-N, NO₂-N, DON and phosphorus were less than 0.5, which indicated their behaviors were non-conservative. Their concentrations were affected by river input, human activities, offshore input and biogeochemical cycle.