After the implementation of the second phase of the 12.5 m-deep channel regulation project in the Lower stretch of the Yangtze River downstream of Nanjing,the effect of channel regulation in the Luochengzhou passage is remarkable with ship traffic increasing and large-scale trend of vessels passing being significant.The navigation environments in the Luochengzhou passage are complex as affected by the sharp curve and high flow velocity at Sima bend,the coexistence of -10.5 m and -12.5 m deep channels,the mixing downstream sailing of large-scale and small-scale vessels and other factors.In the flood season of 2017,there were several cases of large-scale ship grounding accidents owing to sailing out of the -12.5 m deep channel by mistake while sailing upstream.According to the analyses of riverbed evolution,flow field and navigation behavior,this paper proposes the following optimization measures to be taken in the Luochengzhou passage:to realign the layout of the main channel to the left,add an additional recommended downstream route to realize the separate sailing of large-scale and small-scale vessels,apply virtual aids to navigation,and optimize the existing waterway regulation projects,to further establish a safe and efficient navigational pattern.