Abstract: With the development of economy and the society, the deficit in water resources has increasingly arisen in many cities. In the paper, a risk model for the dam of Rizhao Reservoir was established by using the theory of overtopping risk analysis against simultaneous actions of flood series and wind wave series during flood period. Through considering thoroughly the uncertainties of flood, wind, reservoir storage volume and discharge capacity, then, the model was applied to Rizhao Reservoir to compute its pertinent overtopping risk and safety reliability under the original flood series and regulation scheme, and thereby a evaluation of overtopping safety of Rizhao Reservoir was made. Besides, in order to utilize efficiently the valuable water resources (including flood water resources) upstream of Rizhao Reservoir, a new regulation scheme with an overtopping safety reliability over 99.999 % was recommended by the author thorough comparisons according to the downstream discharge capacity and related area to be drowned. Thus, more remarkable economic will be obtained while any new investment is not needed to the Reservoir Administration.