The rapid economic development of the countries worldwide has caused a considerable increase in marine transportation of raw materials, especially of crude oils in offshore activities. However, a significant amount of oil comes into the sea from operational discharge of ships as well as from incidents such as collisions， groundings and contacts. Crude oils contain a wide array of toxic substances such as benzene, toluene, xylene, and other low-molecular-weight aromatics. Marine fauna and flora are highly susceptible to the toxic effects of oil and oil fractions. It thereby poses an immediate threat to fisheries resources. The purposes of this study is to investigate the methods of treating oil spill incident of ships. Various factors which need to be taken into account in the development of techniques and in the design of equipment for dispersant application and mechanical recovery at sea are discussed. Dispersants are tested for efficiency and toxicity，and are used in such a way as to achieve maximum benefit for minimal risk of biological damage. Mechanical recovery is also available but its use is restricted because of low encounter rate, wave interference and viscosity limitation. Finally, it is shown that better navigation other than better technical precautions or better developments in ship building is the most effective measure for preventing accidental oil pollution.