The interaction between vegetation and sediment dynamics and its function in driving saltmarsh evolution receives increased attention from geomorphologists and ecologists.  Once the saltmarsh is invaded by exotic species, the bio-physical interaction is expected to be modified and consequently, the competition between native and exotic species co-drives the saltmarsh evolution. The pioneer zone of a saltmarsh is occupied by the presence of dynamic vegetation patches or tussocks. As the saltmarsh extends, the patches merge together to form homogenous covers. The successive invasion of exotic species also appear in an initial form of patches. Therefore, in order to understand the saltmarsh evolution, it is fundamentally important to compare the vegetation-sediment dynamic interactions between native and exotic species at a scale of patches. Saltmarshes developed on the mudflat of the Andong Shoal, Hangzhou Bay, provide a specific example of rapid evolution of saltmarsh, in association with typical native (Scirpus mariqueter) and exotic (Spartina alterniflora) species in China. The purpose of this study is to investigate the saltmarsh evolution driven by native and exotic species from a perspective of biomorphodynamics. High resolution (~1m) remote sensing images were collected for large scale vegetation distribution analyses. In situ observations of sediment dynamics at a relatively smaller scale were conducted in succeeding seasons, comparing the bare mudflat, the vegetation patches and the gap between neighboring patches. In addition, in situ biological investigations and geomorphological surveys were undertaken. The preliminary results revealed that: 1) the patches of Spartina alterniflora appear on both the pioneer zone and the high marsh and unlike the native species, they do not follow a self-organization pattern; 2) the Spartina alterniflora is better at trapping sediments, but Scirpus mariqueter is better in attenuating turbulent energy; and 3) the patch-sediment dynamic interaction is found to be size-dependent and this is likely to be the key of driving saltmarsh evolution.