Abstract: Riverbed incision at the downstream of the dam would induce fall in water level and water level fluctuation. As a result， the original energy dissipater of the dam can not be able to dissipate water power completely. Rising water power will destroy the energy dissipation structure. An energy dissipation structure having two steps is used in the Xiaobudong rubber dam. Due to excessive sand mining， the riverbed was sharply incised for successive years， the energy dissipation structure was thus destructed. The structure was reinforced many times， but during a heavy flood the energy dissipation structure between the first stilling pool and the second still pool was destroyed around the whole dam line, which brought huge economic losses and threat to the Xiaobudong rubber dam. In this study， based on hydraulic experiments, the failure of the energy dissipator of the Xiaobudong dam is analyzed. The connection section between the first and second energy dissipaters has been re-designed， and as a result, in the first and second stilling basins, stable hydraulic jump, is formed, and the energy dissipator is found in good condition. Besides， the limit depth of riverbed incision is also studied. After reinforcement measures are actually implemented， the energy dissipator of the dam is able to dissipate the water power completely， and the energy dissipation structure suffers no damage again. The ideas and measures of the reinforcement in this study can provide a reference for other energy dissipators facing the similar threat caused by riverbed incision.