Abstract: The FFBR (flexible fast breeder reactor) is a sodium-cooled fast reactor with flexible breeding ratio (BR) from 1.1 to 1.4. It realizes flexible breeding in one designed fast reactor core without changing the pool structure, fuel design and control system arrangement. Comparing with traditional fast reactor design, this concept enables fast reactor to respond to the industrial needs effectively. The transition scheme is necessary to convert the BR when the breeding requirement changes. The feasibility research of transition scheme was performed to convert the BR from 1.1 to 1.4 and inverse from 1.4 to 1.1, since these two processes appear to be the most challenging transition situations. All the results show that it is feasible to convert the breeding ratio of FFBR through refueling scheme design.