The Turkish strait is one of the most important routes of oil transportation. It connects the Black Sea and the Mediterranean, and it enables to transport the oil produced in the north of Black Sea to Europe directly. Istanbul city which has thirteen million of inhabitants has been large accidents. The tanker accident in Istanbul strait can be a great disaster that directly attacks on the life in city. The oil spill problem originated from tanker accidents is one of the major topics in Turkish straits. This paper describes the numerical simulation of oil spill in Istanbul strait for that enables us to estimate the effect of oil spill if tanker accident occurs. The output of the numerical simulation can be used to define and specify the proper methodology and procedures for the "Oil Spill Contingency Plan of the strait of Istanbul".