Zinc-ion　hybrid　capacitor　(ZHSC)　is　recognized　as　a　favorable　energy　storage　device　due　to　the　combined　advantages　of　battery-type　anode　and　capacitor-type　cathode.　However,　it　still　remains　a　huge　challenge　to　achieve　a　high-specific-capacitance　cathode　without　compromising　the　rate　capability　for　high-performance　ZHSC.　Here,　a　three-dimensional　hierarchical　nitrogen　and　phosphorus　co-doped　reduced　graphene　oxide　hydrogel　(NPGH)　is　synthesized　with　small-sized　graphene　oxide　precursors　via　one-step　hydrothermal　reduction　and　in-situ　doping,　which　is　firstly　used　as　cathode　for　ZHSC　without　adding　extra　conductive　additives　and　binders.　In　this　case,　small-sized　graphene　sheets　can　increase　and　shorten　ions　diffusion　channels　for　the　efficient　utilization　of　active　surface　compared　with　commonly-used　large-sized　counterparts.　Moreover,　nitrogen　and　phosphorus　co-doping　can　synergistically　enhance　the　conductivity,　provide　additional　active　sites,　and　promote　the　adsorption　of　zinc　ions,　which　is　well　demonstrated　by　electrochemical　analysis,　ex　situ　characterization　and　DFT　theoretical　calculation.　Attributed　to　the　synergy,　NPGH-based　ZHSC　displays　large　specific　capacitance　(251.3　F　g-　1　,　0.5　A　g-(-　1)　),　outstanding　rate　performance　(79　%,　50　A　g(-1))　and　excellent　cycle　stability.　This　work　proposes　a　novel　strategy　of　tailoring　rGO　cathode　by　simultaneous　size　effect　and　doping　engineering,　which　shows　a　great　promise　of　constructing　high-performance　rGO　based　ZHSC.