Abstract: Based on nutrients and hydrological data of one fixed station and twelve navigation stations in 2018 flood season in the Sansha bay, Fujian province, this paper found: (1) The average concentrations of SiO₃-Si、NO₃-N、NH₄-N、PO₄-P and SSC in ebb (includes drainage of the Ningde city) are about 1.2, 3.6, 6, 2.5 and 2 times higher than that in the flood (seawater) in Dajinxi estuary, respectively. (2)The concentrations of NO₃-N and SiO₃-Si decrease by 31% and 50% with the increased of salinity, the result indicated SiO₃-Si and NO₃-N variation were controlled by river discharge. However, with increase of salinity, the concentrations of NH₄-N and PO₄-P showed a slight decrease trend, and NO₂-N even showed an increase trend, the result implicated that change of NH₄-N、PO₄-P and NO₂-N were mainly controlled by aquaculture in the bay. (3) The average concentrations of inorganic nitrogen (DIN) on twelve navigation stations was 57.33>21.41 μmol/L, PO₄-P (DIP) was 2.28>1.45 μmol/L, and DIN/DIP was between 8～30, such level of above parameters indicated that the water quality in the Sansha bay had exceeded the grade IV water quality standard and reached the state of eutrophication.