Abstract: Reservoirs play a vital role in daily life and regional water resource management. However, under the increasing frequency of extreme weather events, the risk of dam break is rising. Therefore, conducting a pre-event analysis of dam break risk is of great significance. This study takes the Niutoushan Reservoir in Shouning County, Fujian Province as the research object. Various dam break discharge calculation methods were applied to determine the most critical dam break outflow scenario.The TELEMAC-2D Model was used to simulate the flood evolution process and obtain inundation data under different dam break scenarios. Simulation results show that, under the worst-case scenario, a dam break at Niutoushan Reservoir could potentially affect 10 580 people and cause an estimated economic loss of approximately 135 million yuan.The outcomes of this study can provide technical support for emergency response to sudden incidents and serve as a reference for relevant management departments in developing disaster prevention and mitigation measures.