Abstract: In this paper we take detail analyses on the sediment grain size for three tidal flat sections to set up the diagnostic indexes for recognization of tidal flat facies along the north bank of the Hangzhou Bay. The study also examined the application of the diagnostic indexes for distinguishing salt marsh, upper and lower tidal flats in a Holocene sediment core HZK11. The results show that clay and sand components could be the diagnostic indexes for distinguishing salt marsh, upper and lower tidal flats. Salt marsh volume curves are different from the upper and lower tidal plat. The parameters (Mode, Median and Mode) are effective indexes to identify salt marsh upper and lower tidal flat sediments.Above diagnostic sediment components, grain size parameters and volume curves are applied successfully to identify the exact tidal plat facies in boreholes and can be used to reconstruct relative sea-level which demonstrates sea-level rise of around 1.2 cm/a from 9700 cal a BP to 8700 cal a BP.