Abstract: The symbiosis relations between ports and shipping insurance services, ports and shipping brokers in a shipping cluster and their dynamic evolution are analyzed by means of Lotka-Volterra model. The situation in Guangzhou is investigated in particular for illustration. The research shows that the mutualistic symbiosis of those units has been developing. Shipping insurance services and shipping brokers, as high-end shipping services, have benefited from the development of Guangzhou Port. The development of the port has been the driving force of the shipping cluster. As the shipping cluster upgrades and those high-end shipping services become its core competitive power, the roles of ports will change. This research provides some clues for port management.