Aiming at the problem of insufficient ship service capacity in the middle reaches of the Yangtze River,we study the variation characteristics of the capacity and composition of the passage vessels to improve the channel service level and shipping economic benefits.Through field investigation and statistical analysis,it is found that the average annual decline rate of total flow of service vessels in the middle reaches of the Yangtze River is 1.8%,the average annual increase rate of the total net load tonnage is 9.0%,and the average annual large-scale rate of vessels is 11%.With Chenglingji section as the boundary,the ratio of average daily flow of vessels in the upper and lower reaches is 12.2,the proportion of vessels with more than 5,000 tons in the upper reaches grows continuously,and the proportion of vessels with less than 5,000 tons is constantly increasing.The proportion of vessels with more than 10,000 tons in the following sections grows continuously,while the proportion of vessels with less than 10,000 tons declines continuously.It can be seen that with the improvement of waterway conditions in the middle reaches of the Yangtze River,the large-scale vessel becomes more significant,and therefore higher requirements are put forward for the waterway regulation.