In order to study the impact of tailings reservoir dam failure on downstream villages，the effectiveness and necessity of engineering measures are analyzed by comparing the changes in the flow rate of the point before and after the engineering measures are taken and the flow rate through the section.In this paper，an actual tailings reservoir is used as an example to simulate three-dimensional numerical values through FLOW-3D software.Taking a tailings reservoir as an example，a three-dimensional numerical model of the physical terrain and houses and villages within 3 km of the tailings reservoir and its downstream is established，and the dynamic process of the gradual dam failure of the tailings reservoir is simulated.And on the basis of the original tailings reservoir model，a dam is added at the foot of the dam to compare and analyze the impact of dam failure on the downstream.The results showed that after the engineering measures were taken，the water level of the monitoring point decreased significantly，the flow rate of the section flow slowed down，and delays the section time at which the maximum flow rate occurs.It is proved that the engineering measures are effective.