The method, using slope buckling safety factor to measure the degree of dam-break hazard, results in the unscientific conclusions of identical dam-break risk with respect to the desolate & uninhabited gobi desert and densely populated & highly economic-developed city. On the basis of vulnerability theory, a dam-break hazard vulnerability assessment index system, which comprehensively considering the inherent risks of dam-break and the intrinsic vulnerability of hazard-affected bodies, was established. The production of dam-break hazard-causing factor intensity, including the current dam height, reservoir capacity & downstream main ditch longitudinal, and accident probability by the Monte Carlo method is the inherent risk level of dam-break. The result by the multiplying physical exposure and the intrinsic vulnerability, including household fitness index & the emergency self-help index, as well as the disaster relief capacity is the hazard-affected body vulnerability. Results are contributable to further consummate the vulnerability risk assessment technology and the reliability of dam-break hazard.