Abstract: Due to sediment retention effects of reservoirs group in upper Yangtze River and reduction of sediment entering the Three Gorges Reservoir after operation of Three Gorges Project, significant decay of sediment discharge and severe river channel erosion are developing at the downstream of Three Gorges Project, reaching a accumulative 1.6 billion m3 erosion quantity from 2002 to 2015. At the same time, the bankfull river geometry also changed. For better mastering the river adjustment condition in the middle Yangtze River reach, we calculate the mean bankfull river geometric parameters in reach scale by statistics. We establish an empirical relation between these parameters and mean erosion intensity in flood season of previous 5 years, and based on this we carry out back analysis on the bankfull river adjustment process along with the water-sediment change. Aiming at the high frequency bank collapse in the middle reach after the operation of TGP, we summarize the temporal and spatial characteristics of river bank collapse, and confirm that the increase of erosion intensity is the main reason that induces river bank collapse.