To analyse the impact of the ecological protection project construction of Qiujiazhou on the channel navigable flow conditions in the Ganjiang River,this paper establishes a two-dimensional hydrodynamic mathematical model of the tail reaches of Ganjiang River based on TELEMAC software.The calibration is verified through measured hydrological data,and the hydrodynamic process before and after the implementation of the project is simulated under five typical working conditions.The influence of the project construction on the hydrodynamic and navigable flow conditions of the Qiujiazhou section of the river is analyzed.The results show that after the implementation of the project,the overall flow pattern of the river section is stable,with no significant changes compared with before the project,and no adverse flow conditions such as obvious backflow occurred.The maximum flow velocity decreased from 2.1 m/s to 2.0 m/s,a decrease of about 4.67%.The variation of flow velocity shows spatial differences,among which the flow velocity in the vicinity of Laoguanzhou increases due to dredging under the condition of floodplain water flow,with a maximum increase of about 0.1 m/s,and the increase weakens with the increase of flow rate.Before and after the project,the maximum longitudinal flow velocity of the channel is lower than 2.0 m/s,and the maximum transverse flow velocity of individual sections is slightly higher than 0.5 m/s under the high flow condition.The implementation of the project has a limited impact on the navigable flow conditions of the channel and will not have obvious adverse effects.The study can provide scientific support for the safe operation and maintenance of Ganjiang River waterway.