Abstract: Samples of the same original sediments experienced different intensive hydrodynamic action were selected on the tidal plat of subaqeous delta of Yellow River, China, to research the transform of soil microstructures induced by wave action. We took undisturbed soil samples with light drilling machine and analyzed their microstructures features with SEM,and found some special and interesting phenomena of wave reformed microstructures of deposited sediments on the seabed by wave,including various aspects such as the content, distribution and exiting situation of fine grain component, the grain uniformity, the grain shape, and the arrangement of sediment grain. However, the mechanism of these microstructure transform is not clear now, but may be related to heterogeneous liquefaction or thixotropy of the silt in Yellow River Delta.