The Cao’e River gate has been in operation since the end of 2008. The gate is normally closed for storage and opened for drainage during flood seasons. The river channel on the gate has changed from “scouring during the flood and silting during tide”to “single-direction scouring”，and the riverbed has undergone a large change. In this river environment，one of the most important restricting factors for the bridge construction is the navigable flow conditions，which are mainly the river regime，flow velocity and flow pattern conditions of the project reach，and the influence of the bridge construction. In this paper，the current situation and trend of the river regime of the project reach are analyzed based on the topography of many years after the gate was built，and the flow velocity in the channel is calculated and analyzed by establishing a plane two-dimensional mathematical model. The study shows that：1）Without the interference of large human activities，the river regime of the project reach is stable and the pattern of the beach channel will not change. 2）The flow velocity pattern meets the navigation requirements under the navigation high water level，and the construction of the bridge will have little impact on the channel . Therefore，it is feasible to build bridges in this reach.