Port activities and urban activities can both promote each other and restrict each other.The land transportation system carrying both activities is crucial to the development of the port city. Based on the development examples of domestic and international port-cities,and studying the spatial expansion mode of the port-city,we find that the problem of transportation system constraints is widespread in the rising stage of the port-city,and the key influential factors are obtained as follows:1)the matching between the traffic demand hierarchy and the traffic diversion of the transport system;2)the coordination of traffic system and land use layout;3)the matching between the port size and the number of transport channels.Combining with the case analysis,we carry out qualitative and quantitative analyses.