Abstract：Full investigation and comprehensive analysis have been conducted on the bank slope ecological geo-environment in the Jinsha River, Yalong River and Dadu River hydroelectric project areas and main problems in the eco-environmental geology and environmental evolution effect. On that basis and according to the classification assessment concept and principle, the authors have explored the concept and method of assessment of the effect of cascade hydropower development on the ecological geo-environment in the drainage basin, established an assessment system of the effect of cascade hydropower development on the ecological geo-environment, which consists dominantly of four major subsystems, namely, the assessment subsystem of slope (bank slope) stability, assessment subsystem of soil erosion and reservoir sedimentation, assessment subsystem of the eco-environmental evolution and subsystem of the influence of social economic development, initially established four major assessment index systems and discussed the assessment method and expression way of assessment results for discussion.