Polyaniline-modified　renewable　biocarbon　(ACPANI)　composites　were　prepared　via　static　low-temperature　in　situ　polymerization　of　aniline　monomers　on　the　biomass-based　porous　biocarbon　(AC)　that　was　derived　from　watermelon　rind.　In　the　ACPANI　composites,　the　AC　biocarbon　was　served　as　a　three-dimensional　supporting　skeleton　for　polyaniline　(PANI)　to　provide　a　large　accessible　surface　area,　and　PANI　was　used　to　improve　their　electrochemical　performances.　The　porous　AC　biocarbon　was　coated　with　nanofibrous　arrays　of　PANI　via　electrostatic　interaction　and　van　der　Waals　forces.　The　ACPANI-2　composite　that　obtained　with　an　AC/aniline　mass　ratio　of　20:80　exhibited　an　excellent　electrochemical　performance　as　a　hybrid　electrode　for　supercapacitor.　A　superb　specific　capacitance　of　520 F g−1　for　ACPANI-2　was　achieved　at　a　current　density　of　1 A g−1,　and　a　high　cycling　stability　with　a　retention　rate　of　capacitance　of　71.2%　after　5000 cycles　was　confirmed.　Furthermore,　an　asymmetric　supercapacitor　using　ACPANI-2　as　a　positive　electrode　assembled　with　the　AC　negative　electrode　acquired　a　cell　voltage　of　1.4 V　and　a　high　energy　density　of　29.3 Wh kg−1.　Therefore,　the　ACPANI　composite　is　suggested　to　be　a　promising　candidate　for　electrochemical　supercapacitor.　©　2019,　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.