Considerable,　attention　has　been　focused　on　transforming　graphene　(GR)　into　semiconducting　GR　by　diverse　strategies,　which　can　perform　as　one　type　of　promising　photocatalyst　toward　various　photoredox　reactions.　Herein)　we　report　a　facile　alkali-assisted　hydrothermal　method　for　simultaneous　tailoring　of　the　lateral　size　of　GR,and　nitrogen　(N)　doping　into　the　GR　matrix,　by　which　small-sized　N-doped　GR　(S-NGR)　can　be　obtained.　For　comparison,　large-sized　N-doped　GR　(L-NGR)　has　also　been　achieved　through　the　same　hydrothermal　treatment　except　for　the　addition　of　alkali.　The　photocatalytic　activity　test　shows　that　S-NGR　exhibits　much　higher　activity　than　L-NGR　toward　the　degradation　of　organic　pollutants　under　visible-light　irradiation.　Structure-photoactivity　correlation　analysis　and　characterization　suggest　that　the　underlying　origin　for　the　significantly　enhanced　visible-light　photoactivity　of　S-NGR　in　comparison　with　L-NGR　can　be　assigned　to　the　lateral　size　decrease　in　the　NGR　sheet,　which　is　able　to　tune　the　band　gap　of　semiconducting　NGR,　to　facilitate　the　separation　and　transfer　of　photogenerated　charge　carriers,　and　to　improve　the　adsorption　capacity　of　NGR　toward　the　reactant.　It　is　expected　that　this　work　will　cast　new　light　on　the　judicious　utilization　of　semiconducting　GR　with　controlled　size　modulation　and　heteroatom　doping　to　tune　its　physicochemical　properties,　thereby　advancing　further　developments　in　the　rational　design　of　more　efficient　semiconducting　GR　materials　for　diverse　applications　in　photocatalysis.