The section from Wenyan to Babao is located at the mouth of Qiantang River,the riverbed undergoes severe erosion and siltation,and the water depth is greatly affected by the terrain,which directly affects the navigation of ships.In addition,the calculation of navigation guarantee is complicated due to the influence of upstream runoff and tidal bore.Therefore,this paper analyzes the actual navigation guarantee rate of the Wenyan to Babao section of Qiantang River using the underwater terrain of various years since 2007,taking into account factors such as tidal bore,runoff,and water depth.The results show that during the period from 2007 to 2020,the navigation guarantee rates under the water depth of 3.8 m,3.5 m and 3.2 m are 60.1%-79.8%,71.9%-87.5%,and 81.1%-97.0%,respectively,which is consistent with the reality.The research method is of reference significance to the analysis of navigation guarantee rate in estuarine areas with large changes in riverbed erosion and sedimentation,and complex dynamic conditions.