Abstract: The dam risk criteria, design methodology of risk control, and design safety index system of cascade reservoirs are essential to the safety management of a river basin. In this paper we systematically examine previous studies in China and overseas, and suggests an acceptable social risk criterion of 10-6/a and a tolerable social risk criterion of 10-5/a for cascade reservoirs. We also present a trinity design methodology of “safety factor - reliability index - annual failure probability” based on the current methods of project design, the theories of safety margin ratio, and the Bayesian network. According to its grading standard and risk control functions in the river basin, a hydropower project can be defined as a “special class project”, if it satisfies: dam height greater than 200 m and water storage capacity larger than 1 billion m3, or its dam break will cause the First Class dam break in the downstream. For this special class, we suggest a risk control standard: annual failure probability of (1.0-5.0) ×10-8 and reliability index of 4.45-4.70, and construct a system of risk design indexes including the design standards for flood control, seismic resistance, dam reserved free board, and flood discharging capacity. The results of this study would fill the gap in the standards for safety design of super-high dams over 200m high and help the research on risk control theories and design of cascade reservoirs.