Abstract: The GeoDam-BREACH toolsets are used to simulate the process of the dam-break flood routing downstream of the Xiaojinggou reservoir under the conditions of super-standard flood. The inundated area and water depth distribution of the inundated area downstream of the dam breach are obtained. Then the analysis of the life loss risk caused by the dam breach is carried out by Graham method in this study. The analysis results show that the reservoir dam-break flood will give serious impacts on the downstream area, where the villages and towns may be at risk of flooding; and the mortality rate of population at risk in the downstream dam-break flooding area is higher and increases with the decrease of warning time. Therefore, it is concluded that the warning time and understanding of the dam-break flood severity are important factors affecting the loss of life. And the daily inspection work and early warning system of the reservoir dam should be strengthened. The research results provide effective technical support for flood control dispatch and emergency plans compilation of the Xiaojinggou reservoir, and have certain reference values for flood control and dam safety management of similar reservoirs.