For the channel expansion project of the mature seaport area,the surrounding channel network and the navigation conditions of the seaport area are complex.The demonstration of the scale of the channel expansion project should focus on the adaptability of the channel and seaport development.It is difficult to solve the adaptability problem of the construction scale of channel expansion project by traditional static estimation or queuing theory calculation methods.Considering the randomness,dynamics and complexity of the port and shipping system,this paper establishes a simulation model of the port and shipping system based on the Flexsim platform and the characteristics of the navigation environment.The model can simulate the whole process of ship entry and exit operations.In addition,this paper takes the public channel of a major port along the coast of South China as the research object,and selects the indicators to comprehensively compare the scale of waterway expansion,such as the service level of the channel,the proportion of the number of ship delayed,and the delay time of ships.Then,on the premise that the navigable level of the channel in the future is not lower than that of the current channel,the recommended expansion scale is proposed.The research results can provide reference for the design of the scale of public channel expansion project in coastal ports.