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Seven cores were collected from different sediment zones of tidal flats at Xin-yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of 137Cs and 210Pb analysis were carried out for these cores. Sediment rates of the cores and radioisotopes distribution in surface sediment in different zones of the tidal flat were calculated from the 137Cs and 210Pb activities in sediments cores. The results indicated that each tidal zone had experienced different evolution phases,hydrological dynamics in the tidal flats made the grain-size of the surface sediment change gradually. 137Cs and 210Pb ac-tivities on the superficial layer of the cores varied spatially and the reason was discussed. On tidal flats,the fluctuation of 137Cs and 210Pb activities in the cores reflected the special sedi-mentary characteristics. Vegetation affects the grain-size distribution and the vertical profiles of 137Cs and 210Pb in the upper depths. 137Cs and 210Pb chronology got the comparable av-erage sediment rates on the tidal flat. The characteristics of 137Cs and 210Pb in the cores re-flected various depositional dynamical environments in different tidal zones and gave infor-mation on the different evolvement phases of the tidal zones. Based on the information of grain-size distribution,texture of the cores,sediment rates and topography,the evolution lines of the tidal flat were reconstructed.