C₅ fraction is rich in diolefins, including isoprene, piperylene, and dicyclopentadiene. These diolefins play an important role in fine chemicals. The extraction separation system in a C₅ separation unit of SINOPEC has shortcomings such as short operating cycle, which seriously affects the economic benefits of the unit. After comprehensive analysis and demonstration, it is concluded that the design defects of process equipment, the chemical performance, the parameter control, the poor quality of circulating solvent and the high content of free oxygen and water in the system are the main factors restricting the length of operating cycle. Technical research has been carried out to solve the above problems, and good results have been achieved. The operation cycle of the extraction system is greatly prolonged, the parameters of the system are within a reasonable range, the loss rate of target products is low, and the switching cycle of equipment is normal.