A　one-step　salt　melt　assisted　thermal　polymerization　for　the　synthesis　of　nitrogen-rich　water　soluble　graphitic　carbon　nitride　(WS-GCN)　is　presented.　The　as-prepared　WS-GCN　shows　strong　tunable　excitation-emission　pathways　that　have　multi-colored　photoluminescence　from　blue　to　green　with　extremely　high　absolute　quantum　yields　(AQY)　of　22%,　which　is　almost　6　fold　of　pristine　graphitic　carbon　nitride　(GCN)　nanosheets.　It　also　shows　significant　red-shift　of　response　edge　benefiting　from　the　narrowed　band　energy,　due　to　the　feature　of　N-defected　surface　and　N-rich　inner　of　WS-GCN.　After　being　decorated　onto　TiO2,　the　WS-GCN　endows　a　great　enhancement　of　NO-photodegradation　under　visible　light　irradiation,　5.5-fold　increase　to　comparison　with　what　the　pristine　GCN　does.　Further,　the　starting　edge　of　photocatalysis　is　enlarged　to　about　650　sun　for　TiO2/WS-GCN　from　about　450　nm　for　TiO2/GCN.　This　is　ascribed　to　both　enhanced　light-response　range　and　efficiently　restraining　the　radiative　transition　probability　of　WS-GCN　owing　to　the　migration　of　photoinduced　electrons　from　the　CB　of　WS-GCN　to　TiO2.　This　multi-functional　material　may　provide　a　way　for　the　development　of　bio-imaging,　file　secrecy　and　broad　absorption　photocatalysts.