Abstract:Based on the four cruises carried out from July 2006 to October 2007 in the northern Yellow Sea(NYS), the water masses in four seasons in the NYS were classified, and the chemical properties in different water masses were discussed according to the temperature and salinity data. Then the nutriment structure in every season in NYS were analyzed. The results showed that the northern Yellow Sea water can be classified into 4,7,5,5 water masses each season；Coastal water in southern Liaoning (Ys1) and Yellow Sea water masses were present all year round; Yalu River freshwater and the Yellow Sea cold water mass（YC）disappeared in winter; Yellow Sea and Bohai Sea mixed water mass disappeared in autumn; Other water masses were seasonally presented. In the duration of the YC, its internal concentration of nutriment was at a high level, especially in fall, with PO4-P up to 0.9 μmol /L.
