Abstract: Using the data of years, including the latest in situ data observed in Meimaosha and adjacent water areas in the southern passage of the Yangtze Estuary in Sep., Dec. 2003 and Jan. 2004, characteristics of hydrology and sediment were studied by the multi-methods of hydrology, sediment transportation and statistics. The results show that tidal currents show a strong ebb dominance as velocity of the ebb current is larger than the flood current, time of the ebb current longer than the flood current. In general, the average suspended sediment concentration is 1.40 kg/m3 during the period of the spring tide and 0.60 kg/m3 during the period of the neap tide respectively. The observed data also show that suspended sediment concentration during the flood season is higher than that of during the dry season. Suspended sediment concentration of the flood tide is higher than the ebb tide in the spring tide during the flood season, which is contrary in the neap tide. During the dry season either in the spring tide or in the neap tide, suspended sediment concentration of the ebb tide is higher than the flood tide. The change of the suspended sediment concentration gradient is evident. The variety of the current velocity and suspended sediment concentration after the ecotypic reservoir project have been constructed with the current continuity equation and a linear regression formula of sediment carrying capacity. The result show that it will affect the Nanhui tidal flat in a certain extent.