The　bulk　nanocrystalline　SmCo5　sintered　magnet　was　prepared　by　spark　plasma　sintering　technique　(SPS).　The　structure　and　magnetic　properties　of　the　magnet　were　studied.　XRD　patterns　show　that　the　mill　powder　exhibits　amorphous　structure　and　the　magnet　exhibits　CaCu5　structure.　TEM　observation　indicates　that　the　microstructure　of　the　magnet　is　composed　of　SmCo5　single　phase　grains　with　an　average　grain　size　of　30　nm.　The　magnetic　measurement　shows　that　the　coercivity　of　the　magnet　reaches　as　high　as　2.28　MA/m.　The　high　ratio　Mr/Ms　of　0.7　demonstrates　the　existence　of　strong　intergrain　exchange　coupling　among　the　nanograins.　The　magnet　exhibits　a　good　thermal　stability　with　coercivity　of　0.72　MA/m　at　773　K,　and　the　coercivity　temperature　coefficient　β　of　-0.146%/K.