Based on the ship flow data of the 12.5 m deep water channel of the Yangtze River below Nanjing and the tide level data of various hydrological stations along the route,based on the theory of traffic flow,and combining with the hydrological analysis,we study the flow and flow characteristics of the 12.5 m deep water channel Yizheng,Dantuzhi,Kouanzhi,Fujiangsha,Nantong waterway.The results show that the big ships account for 73.2% in Yizheng channel’s ascending vessels,the big ships and the boats account for the same proportion in Kouanzhi channel,the big ships account for about 33% in Dantuzhi,Fujiangsha and Nantong waterwaysr.As for the descending vessels,the big ships account for 31.5%～41.3% in all the channels.The ship flow is greatly affected by tides during the spring tide,and the hourly flow of the ascending ships is positively correlated with the tide level.The descending ship is affected obviously by the ebb tide,and the relationship between the upper and lower ships and the tidal level process is unobvious during the small tide.The daily number of ships within a month is not directly related to the tides.The research results may serve as reference for the development of deep channel maintenance and navigation safety plans.