Abstract: In order to realize on-line separator maintenance at one certain floating production storage unit, the scheme of carrying out on-line bypass of primary and secondary separators was researched based on the characteristics of its oil treatment process. The safety risk of looser saturated vapor pressure index was verified by conducting combustible hydrocarbon diffusion analysis in Fluent. Sequential bypass maintenance of primary and secondary separators was realized with piping connection. In addition, the production and operation parameters were adjusted by means of HYSYS simulation to satisfy the requirements of stabilization. It is indicated that the on-line separator maintenance scheme ensures the on-line maintenance of the oilfield, enhances the flexibility of oil treatment system in actual production and operation, brings greater economic benefits, and provides the beneficial reference for the process design of oil treatment system.