For segment floating transportation, Nanchang Bridge and segment turning area are the key points for Honggu Immersed Tunnel in Nanchang. The characteristics of water resistance during floating transportation of the segment are analyzed by Fluent and MIKE fluid dynamics software, so as to guarantee the safe floating transportation. The characteristics of water resistance when the segment passes through Nanchang Bridge are obtained. The characteristics of water resistance at segment turning area are obtained by analyzing water resistance coefficient Cw and the flow field under different hydrological conditions. The results can provide reference for water resistance calculation during floating transportation of immersed tunnel segment.