A large quantity of cargo flow among wharfs in large and wide port, which make bad inflences not only upon the transportation efficiency, but also upon the environment to the surrounding area.
　For the purpose of the reduction of these cargo flows, this paper has proposed a model which simulated a daily cargo flow and vessels movement in port.
　This model can estimate whether cargo flows among wharfs increase or decrease, under many cases of plan or policy.
　Usefulnesses of this model are shown by the application to Yokohama port.