Abstract: The Qimu Island-Diaolong Cape region is famous for its unique barrier-lagoon coast. The coastal sedimentary environment and sediment transport directly influence the coastal morphological evolution. As far as human activities are considered, more attention shoud be paied to the coastal environment. Surface sediments were sampled off (0~12 m) the Qimu Island-Diaolong Cape in December, 2010. Sediment grain sizes were tested using Laser Diffracting and screening Method. Sediment types were named after Folk et al. (1970) s classification and grain-size parameterse calculated with Fork-Ward method (1957), which have been proved to be more suitable for understanding sediment dynamics. In terms of spatial distribution, the surface sediment is getting finer off the coast. under the dynamic influenc of local environment(water depth, sediment sources, hydrodynamics, et al.). Bed-load dominates the nearshore sediments with a peak value at 71~63 μm, indicating strong hydrodynamics composed of strong waves and longshore currents. The results of GSTA (grain size trend analysis) Model indicates that seabed sediment transport alongshore towards southwest direction. In addition, the influence of underwater topography and river's input is obvious. Vectorial resuls reveal an anticlockwise circumfluence in the southern Shihu Cape.