As one of the regimes subject to dramatic changes in lower Jingjiang reach, Jianli reach is to see a more obvious erosion and deposition adjustment due to reduced release of sediment after the operation of the Three Gorges Project(TGP). In this paper, the possible erosion and deposition of riverbed and regime change in Jianli reach during the initial operation stage of TGP were computed and studied using a 2-dimensional mathematic model of flow and sediment. The study showed that the overall regime changed slightly, while there were drastic erosion and deposition of riverbed as well as deepened scour depth of the crosssection. In addition, parts of the bank section and the right edge of Wugui sandbar declined and collapsed, and the left branch of Wugui sandbar shrinked while the right branch expanded，and the point bar of new sandbar was showing a tendency of being cut-off.