Abstract: After the completion of the Hagedagou Bridge in the reservoir area of Lianghekou Hydropower Station, a weak and broken layer was foundat the bridge foundation slope on the right bankthrough exploration.After the reservoir impounding, the bank slope has the risk of creep deformation and local instability under the effect of repeated drawdown and immersion softening of reservoir water.Considering the interaction between the bank slope rock mass and the bridge foundation under the environment of water drawdown, a slope stability calculation model and design conditions of the river-crossing bridge were constructed.At the same time, the stability of bridges and bank slopes was analyzed by the Morgenstern-Pryce method.The results show that the shallow unloaded loose rockmass in the bridge site of the right bank slope may produce deformation instability after reservoir impounding.In order to prevent the influence of rockmass deformation and instability on bridge pier platform, comprehensive reinforcement schemes of anti-slide pile + anchor cable and frame beam + anchor cable were proposed.The treated Hagedagou Bridge has undergone a reservoir water level uplift test of nearly 100 m.And there is no obvious deformation of the bridge and slope, and the monitoring data meet the design requirements, which has ensured the safety of the reconstructed highway during the reservoir impounding and operation period.This case can provide reference for similar engineering treatment.