Abstract: The large-scale application of the dispersant is often used as an emergency in the current process of dealing with marine oil spill.The physical and chemical properties of dispersed oil are greatly changed compared with original oil, which will have a series of effects on the fate behavior of spilled oil in the sea.This paper analyzes the positive role and limitations of the application of dispersant in accidents of oil spill:The crude oil is emulsified and dispersed into small oil droplets in seawater, which increases the degree of confusion of the system, the physical transport process is more complex; The physical and optical properties of dispersed oil are changed, the photochemical transformation of petroleum hydrocarbons is tended to be more easy; The dispersant will affect the biodegradation of spilled oil, but their facilitating and inhibiting roles are still unclear; Chemical dispersant has biological toxicity, and the toxicity increased when it combined with spilled oil. Environment friendly biosurfactant is an effective alternative to chemical dispersant.Setting up the mathematical model of the physical transport and accurately evaluating the dispersants effects on the photochemical transformation and biodegradation of spilled oil for providing reference of rational use and accurate evaluation of dispersant are urgent works.In addition, it is also a promising research direction to develop cheap and environmentally friendly bio-dispersant.