Abstract: It is not appropriate to treat with the oil contamination of products for offtake station by blending method. The paper discusses the practicability of modifying the vacuum device of oil recovery unit to a vacuum distillation while performing oil contamination simultaneously. Laboratory observation showed that the diesel flash point reached over 50 ℃ at a vacuum degree of 20 kPa and 25 ℃ with 1 hr of stabilizing time This revealed the viability of distillation by negative regulation. The oil contamination pilot-plant was designed and established. The contamination parameters were determined. The experiment indicated that the plant is able to separate gasoline from diesel. It meets the requirements of diesel quality and storage stability.