Construction　of　metal　oxide/sulfide　and　carbon-based　material　nanocomposites　is　an　effective　strategy　to　obtain　high-performance　electrode　materials　for　supercapacitors.　In　the　present　work,　graphene　oxide　nanofibers　(GONFs)　are　selected　as　the　support　materials,　and　the　nanocomposite　of　reduced　graphene　oxide　nanofiber　and　cobalt　sulfide　(rGONF/CoS2)　is　synthesized　via　a　simple　and　facile　method.　As　an　electrode　material　for　pseudocapacitors,　the　rGONF/CoS2nanocomposite　exhibits　a　high　specific　capacitance　of　635.8 F g-1 at　a　current　density　of　1 A g-1measured　in　6 M　KOH　electrolyte,　which　is　much　higher　than　that　of　bare　cobalt　sulfide.　Furthermore,　the　rGONF/CoS2nanocomposite　has　also　shown　excellent　cycling　performance　with　95.4%　capacitance　retention　over　2000　cycles.　In　addition,　the　assembled　asymmetric　supercapacitor　(ASC)　device　using　rGONF/CoS2nanocomposite　as　cathode　material　and　activated　carbon　(AC)　as　anode　material　can　work　at　a　high　operating　voltage　of　1.65 V　and　show　a　maximum　energy　density　of　13.8 W h　kg−1at　a　power　density　of　824.6 W kg−1.　©　2017　Elsevier　B.V.