A　novel　route　for　the　preparation　of　the　single-phased　Sm2Co17　nanocrystalline　bulk　with　ultrafine　grain　sizes　was　proposed.　It　was　found　that　the　nanocrystalline　Sm2Co17　has　a　hexagonal　crystal　structure　at　the　room　temperature,　which　shows　a　different　thermal　stability　from　the　conventional　polycrystalline　alloy.　The　intrinsic　coercivity　of　the　nanocrystalline　Sm2Co17　with　a　hexagonal　crystal　structure　was　greatly　increased　as　compared　with　the　single-phased　polycrystalline　alloy　with　a　rhombohedral　structure.　The　microhardness　and　the　elastic　modulus　of　the　nanocrystalline　Sm2Co17　bulk　were　increased　as　high　as　1.8　and　2.6　times,　respectively,　when　compared　with　the　polycrystalline　parent　alloy.