In　this　study,　we　report　a　new　strategy　for　preparing　magnetically　anisotropic　SmCo5　single　crystal　particles　by　reductive　annealing　of　precursors　with　specially　designed　nanostructures.　The　precursors　containing　urchin-shaped　Co　clusters　and　Sm(OH)(3)　nanorods　were　synthesized　by　a　hydrothermal　process.　Then　we　coated　these　precursors　of　Co/Sm(OH)(3)　nanocomposites　with　Ca(OH)(2),　and　the　following　thermal　reduction　generated　SmCo5　particles,　where　the　original　size　and　morphology　of　the　precursor　were　basically　preserved　after　undergoing　high　temperature　annealing.　The　single　crystalline　SmCo5　particles　exhibit　strong　magnetic　anisotropy　and　excellent　room　temperature　magnetic　properties:　remanence　of　8.1　kG,　coercivity　of　25.7　kOe,　and　a　maximum　energy　product　of　15.8　MGOe,　which　is　one　of　the　highest　maximum　energy　products　for　chemically　synthesized　nanostructured　SmCo5　particles　presently　reported.