Every planning of a port development or design of a new harbour is confronted with the unique physical properties and related problems to be solved. On the other hand every port can be defined as a link in the transport chain involved in the transfer of cargo from one medium of transport to another. Every port and its connected transhipment equipment and transport means are designed for the same basic purposed and involves a port consists of a number of systems as: a. a system of signals (buoys and navigation aids) to enable the ship to make a safe landfall b. an anchorage for use while a ship is waiting due to tidal conditions or congestion c. pilot system d. a system of towage e. the quays with cargo handling facilities f . undercover and open storage g. inland transport system etc. I t is possible, therefore, to construct an imaginary port which incorporates this features. Nevertheless to determine the capacity of a portsystem, it is necessary to schematize the reality by leaving out all non relevant aspects. A powerful method that can be used in the complicated port systems is offered by the discrete computer simulation. Generally speaking simulation is used to study the dynamic behaviour of the harboursystem by experimentations with a model of that system. In this way it is possible to obtain data which in statistical sense are relevant to the original system.