Oil pollution, which is a major cause to change for the worse of the marine environment, occurs mainly by the accidents such as oil spill during the loading / unloading of tankers at berth and due to tanker strandings or collisions. The damage to the ecological systems and the trouble to the socio-economic balance of local comunity might be caused by the wrong choice of countermeasures to prevent from spreading the spilt oil. Therefore, the prevention systems of oil polution have to be evaluated accurately. Oil pollution is regarded as an very complicated problem due to the many governing factors of which the condition changes rapidly with time. Thus, a dynamical simulation analysis model based on the system dynamics is constructed, in which the conditions due to weathering, diffusion, oil collection process by pollution prevention systems and so on, are considered. As a practical example, a precedent oil spill caused by a tanker collision at sea is analyzed using the proposed dynamical simulation model.