In order to investigate the effect of inflow of Yangze river on the distribution of chlorophyll-${alpha}$, the results of serial oceanographic observation during 2000-2005 were used. The oceanographic conditions in the northern East China Sea is influenced by the Tsushima Warm Current and low saline water derived from the Yangze river. The distributions of these water masses vary significantly by the season in the northern East China Sea. The sea surface temperature and salinity were stable and concentrations of chlorophyll-${alpha}$ were low in the eastern part of $126^{circ}E$. On the contrary, the salinity was significantly influenced by the low saline water derived from Yangze river with the high concentrations of chlorophyll-${alpha}$. It is suggested that the low saline water inflowed from the Yangze river affects high concentrations of chlorophyll-${alpha}$ in the northern East China Sea in summer.