It mainly deals with the separated swimming water in crude oil. The offshore platform water treatment system usually includes an oily sewage treatment system and a water injection system. The conventional oily sewage treatment process is: the oily sewage coming out of the separator first enters the inclined plate oil separator for oil-water separation. Then enter the gas flotation device for separation. If the secondary treatment is not up to standard, a sand filter can be added for tertiary treatment to treat the qualified sewage. Due to environmental protection requirements, the treated oily sewage is usually reinjected into the formation.