It　was　reported　a　facile　strategy　to　fabricate　magnetite　(Fe3O4)　single-crystal　particles　with　critical　single-domain　size　by　employing　graphene　oxide　(GO)　sheets　as　template.　In　this　method,　the　small-sized　Fe2O3　nanoparticles　were　first　synthesized,　and　then　low-temperature　annealing　under　H-2　would　convert　them　into　large-sized　Fe3O4　single-crystal　particles.　The　synthetic　particles　with　an　average　size　of　100nm　exhibit　high　saturation　magnetization　(M-s)　of　0.085Am(2)g(-1),　which　is　very　close　to　theoretical　value,　being　among　the　highest　values　in　ever　reported　for　Fe3O4　made　from　chemical　methods.　On　this　basis,　the　small-sized　Fe3O4　particles　(average　size　of　30nm)　were　also　fabricated　by　coating　with　Na2CO3　shell.