The　introduction　of　graphene　fiber-based　supercapacitors　as　important　power　storage　components　in　wearable　electronic　products　has　attracted　increasing　attention　because　of　their　lightweight,　good　flexibility,　high　power　density,　long　lifecycle　and　excellent　charge/discharge　capacity.　However,　their　capacitance　and　energy　density　are　greatly　confined　as　a　result　of　the　dense　graphene　stacking,　hydrophobicity　and　poor　electrical　conductivity　of　graphene　fiber　electrodes.　Here　we　report　a　nitrogen-doped　graphene　fiber　electrode　with　optimal　micro-/meso-/macro-porosity　ratios　to　improve　the　utilization　efficiency　of　fiber　inner　interface　for　accumulated　charge　storage　and　boosted　ion　transport.　Urea　is　employed　as　both　nitrogen　doping　source　and　self-removed　template　for　graphene　fibers　to　tune　the　hierarchically　porous　architecture,　wettability,　nitrogen　content,　and　electrical　conductivity　for　improved　electrochemical　performance.　The　resulting　supercapacitors　display　superior　areal　capacitance　of　1,217　mF/cm2　(486.3　F/g)　and　high　energy　density　of　27　μW　h/cm2　(10.8　W　h/Kg)　in　polyvinyl　alcohol/H3PO4　gel　electrolyte.　These　metrics　represent　the　highest　values　to　date　among　existing　all-solid-state　fiber-based　supercapacitors　based　on　inorganic　electrolyte.　Moreover,　the　fiber-based　supercapacitors　show　good　rate　capability　and　excellent　cyclic　performance.　Our　work　also　provides　an　understanding　of　the　effect　of　fiber　structure　on　electrochemical　activity　and　highlights　the　importance　of　full　utilization　of　graphene　interior　interface.　©　2021　Elsevier　B.V.