A series of advanced instruments were applied to obtain the field data of bed,bed forms and relevant dynamic factors in the 150 km-long reach of the Changjiang River from Jiangyin to Hengsha Island in March 2002. We found that well-sorted fine sand was in the majority of the bed sediment,which had a median diameter of 2 . Well-developed sandwaves were formed because the grains jumped together on the bed,which was related to the granularity and current velocity during the flood-ebb tidal cycles. A series of advanced instruments were applied to obtain the field data of bed, bed forms and relevant dynamic factors in the 150 km-long reach of the Changjiang River from Jiangyin to Hengsha Island in March 2002. We found that well-sorted fine sand was in the majority of the bed sediment, which had a median diameter of 2. Well-developed sandwaves were formed because of the grains jumped together on the bed, which was related to the granularity and current velocity during the flood-ebb tidal cycles.