Abstract: By using the hydrologic, morphological and geological observations in the Yangtze reach from Zhicheng to Dabujie, cross-section deformation and its spatial variations are examined and responses of water level to this deformation are investigated. The inconsistency in cross-section adjustment in different regions is revealed. In the upper reach, lateral erosion is the major deformation and erosion intensity is greater in an expanding section than contracting section, causing the channel wider and shallower at low level. In the lower reach, down-cut erosion dominates the deformation at all the water levels and the channel develops toward the opposite, narrower and deeper. The difference of the two reaches in dominant deformation is a result of the comprehensive effect of different mainstream swings and riverbed materials. Water level drop caused by erosion under different discharges, is uneven in magnitude over the whole reach, greater in the sections of lateral erosion than vertical erosion. Thus, Changmenxi is a location of deformation transition from lateral erosion to down-cut erosion and the protective measures should be distinguished.