Semiconductor　photocatalytic　technology　has　shown　great　prospects　in　converting　solar　energy　into　chemical　energy　to　mitigate　energy　crisis　and　solve　environmental　pollution　problems.　The　key　issue　is　the　development　of　high-efficiency　photocatalysts.　Various　strategies　in　the　state-of-the-art　advancements,　such　as　heterostructure　construction,　heteroatom　doping,　metal/single　atom　loading,　and　defect　engineering,　have　been　presented　for　the　graphitic　carbon　nitride　(g-C3N4)-based　nanocomposite　catalysts　to　design　their　surface　chemical　environments　and　internal　electronic　structures　to　make　them　more　suitable　for　different　photocatalytic　applications.　In　this　review,　nanoarchitecture　design,　synthesis　methods,　photochemical　properties,　potential　photocatalytic　applications,　and　related　reaction　mechanisms　of　the　modified　high-efficiency　carbon　nitride-based　photocatalysts　were　briefly　summarized.　The　superior　photocatalytic　performance　was　identified　to　be　associated　with　the　enhanced　visible-light　response,　fast　photoinduced　electron-hole　separation,　efficient　charge　migration,　and　increased　unsaturated　active　sites.　Moreover,　the　further　advance　of　the　visible-light　harvesting　and　solar-to-energy　conversions　are　proposed.　©　2021