When the check flood recurrence period of the upstream reservoir in a river is lower than the downstream reservoir，and calculating the check water level of the downstream reservoir，most of the upstream reservoirs have exceeded the check flood standard.In theory，dam overflow will occur，the impact of dam break in the upstream reservoir on flood regulation in the downstream reservoir should be considered.Taking Yaoli Reservoir in Xingan county of Jiangxi province as an example，this paper deduces the inflow flood process under the condition of whether or not the small upstream reservoir breaks，calculates the check flood level under the two conditions through flood routing and obtains the influence of upstream reservoir breaks on the check flood level of Yaoli Reservoir.The results show that the check flood level of Yaoli Reservoir is 0.36m higher than that of non-dam-break when considering the upstream dambreak.The influence of the check flood level should be paid attention to in engineering design and safety appraisal.