Atomic-level　boron　carbon　nitride　nanosheets　(BCNNS)　have　been　prepared　by　a　molten　salt　assisted　assembly　growth　strategy,　which　effectively　promotes　the　solvation　of　precursors,　minimizes　the　surface　energy　and　prevents　the　aggregation　of　layers.　The　as-synthesized　BCNNS　have　atomic　layered　thickness　and　large　lateral　size,　and　show　enhanced　visible　light　H-2　evolution　activity　compared　to　bulk　BCN.