Abstract: During November 2004, surficial sediment samples were collected from the upper part of the tidal flat on the northern bank of Hangzhou Bay. Grain size analysis of the samples, using a Mastersize2000 layer particle sizer, shows that the major constituent of the sediment is silt, with the mean grain size mainly between 5 and 6.5 Φ. The other grain size parameters, i.e. sorting coefficient, skewness and kurtosis, are indicative of the deposit formed in a high energy tidal environment. The sediment is poorly sorted and positively skewed, with a broad kurtosis.Results from the Gao-Collins model for grain size trend analysis show that the sediment transport is directed to west near Haiyan and Luchao Port, but to east between Zhapu and Tuolin. Compared with the residual current patterns in the adjacent waters, the transport trend along the northern bank has the same direction as the residual current. This agreement is related to the inherent relationship between suspended sediment transport and residual currents in this estuarine system, which provides suspended sedimentary materials to the tidal flat.