The　nanocrystalline　Sm2Co17　bulk　was　prepared　by　a　new　developed　method.　The　phase　stability　and　microstructure　were　analyzed　by　XRD　and　TEM　methods.　It　was　found　that　the　nanocrystalline　Sm2Co17　bulk　has　a　hexagonal　phase　with　Th2Ni17　crystal　structure　at　the　room　temperature,　which　only　exists　at　the　high　temperature　in　the　polycrystalline　Sm2Co17　bulk.　The　hysteresis　loops　and　the　mechanical　properties　were　measured　for　the　prepared　material.　The　magnetic　and　the　mechanical　properties　of　the　nanocrystalline　Sm2Co17　bulk　with　the　hexagonal　structure　were　greatly　increased　as　compared　with　the　polycrystalline　alloy　with　the　rhombohedral　structure.