Three-dimensional　(3D)　graphene　materials　have　excellent　electronic　emission　performance　and　mechanical　stability,　showing　significant　advantages　in　the　field　of　high　current　density　field　emitters.　In　this　study,　copper　oxide　modified　three-dimensional　graphene　composites　(LIG/CuO)　are　prepared　in　situ　by　a　femtosecond　laser　one-step　method,　which　realizes　the　simultaneous　regulation　of　cork　carbonization　and　copper　oxidation.　Shallow　copper-rich　precursors　are　constructed　by　copper　salt　infiltration　and　ascorbic　acid　reduction.　Laser　irradiation　is　used　to　synchronously　induce　the　carbonization　of　cellulose　into　few-layer　graphene　and　the　transformation　of　Cu　into　CuO,　forming　a　three-dimensional　fiber　network　of　microcrystalline　graphene　coated　with　CuO　nanoparticles　(30–80　nm).　The　structure　exhibits　excellent　field　emission　performance:　the　threshold　field　of　preparing　pure　laser-　induced　graphene　(LIG)　is　~2.12　V/μm　and　the　field　enhancement　factor　is　~8223.　After　optimizing　CuO　loading,　the　threshold　field　of　LIG/CuO-5　is　reduced　to　1.57　V/μm,　the　field　enhancement　factor　rises　up　to　~8823,　and　the　ultra-high　current　density　of　22.71　mA/cm2　is　achieved　at　2.89　V/μm.　The　density　functional　theory　(DFT)　calculations　show　that　the　electrons　at　the　heterojunction　interface　transfer　from　CuO　to　graphene,　which　reduces　the　work　function　of　graphene　from　4.833　eV　to　4.677　eV,　and　the　band　bending　of　CuO　surface　synergistically　reduces　the　tunneling　barrier.　In　addition,　the　local　electric　field　enhancement　effect　of　CuO　nanoparticles　and　the　optimized　distribution　density　synergistically　increase　the　effective　emission　point　density.　The　performance　improvement　is　mainly　attributed　to　three　synergistic　effects:　1)　the　three-dimensional　porous　graphene　network　provides　abundant　tip　emission　sites;　2)　the　introduction　of　CuO　nanoparticles　reduces　the　work　function　of　the　composite　material　from　4.833　eV　to　4.667　eV,　effectively　reducing　the　electron　escape　barrier;　3)　the　heterojunction　interface　forms　a　directional　electron　migration　channel　under　a　positive　bias　electric　field,　combined　with　the　excellent　conductivity　of　LIG,　which　significantly　improves　the　electron　tunneling　efficiency.　©　2025　Chinese　Physical　Society.