We　report　a　chemical　method　to　synthesize　size-control-lable　SmCo5　nanoparticles　(NPs)　and　to　stabilize　the　NPs　against　air　oxidation　by　coating　a　layer　of　N-doped　graphitic　carbon　(NGC).　First　10　nm　CoO　and　5　nm　Sm2O3　NPs　were　synthesized　and　aggregated　in　reverse　micelles　of　oleylamine　to　form　SmCo-oxide　NPs　with　a　controlled　size　(110,　150,　or　200　nm).　The　SmCo-O　NPs　were　then　coated　with　polydopamine　and　thermally　annealed　to　form　SmCo-O/NGC　NPs,　which　were　further　embedded　in　CaO　matrix　and　reduced　with　Ca　at　850　degrees　C　to　give　SmCo5/NGC　NPs　of　80,　120,　or　180　nm,　respectively.　The　10　nm　NGC　coating　efficiently　stabilized　the　SmCo5　NPs　against　air　oxidation　at　room　temperature　or　at　100　degrees　C.　The　magnetization　value　of　the　180　nm　SmCo5/NGC　NPs　was　stabilized　at　86.1　emu/g　5　days　after　air　exposure　at　room　temperature　and　dropped　only　1.7%　48　h　after　air　exposure　at　100　degrees　C.　The　stable　SmCo5/NGC　NPs　were　aligned　magnetically　in　an　epoxy　resin,　showing　a　square-like　hysteresis　behavior　with　their　H-c　reaching　51.1　kOe　at　150　K　and　21.9　kOe　at　330　K　and　their　M-r　stabilized　at　around　84.8　emu/g.　Our　study　demonstrates　a　new　strategy　for　synthesizing　and　stabilizing　SmCo5　NPs　for　high-performance　nanomagnet　applications　in　a　broad　temperature　range.