Abstract: Accurate assessment of the impact of reservoir discharge is the key basis for optimal scheduling decision-making and downstream disaster prevention and control, which has dual scientific value for identifying flood control shortcomings and formulating control measures. In view of the shortcomings of the current research in the systematic evaluation of discharge schemes and the inversion of critical safety discharge, this study took the lower reaches of Guanting Reservoir in Yongding River as the object. A 1D hydrodynamic model for the 21.113 km river channel downstream of the reservoir was developed using IFMS software, based on the measured topographic and hydrological data. Under 18 different reservoir discharge schemes, the change of water level along the lower reaches of the river and its influence on the villages and roads along the river were analyzed and calculated. The results show that the main objects affected by reservoir discharge are the low-lying sections along the river,Youzhou Village and Anjiaxuan Village. The uninfluenced safety discharges of downstream riverside roads, Youzhou Village and Anjiaxuan Village are 175 m³/s, 1 350 m³/s and 1 980 m³/s, respectively. The research results can provide important decisionmaking basis and technical support for the scientific scheduling and operation management of Guanting Reservoir.