In this paper, a novel fabrication process of the nanocrystalline Sm3Co alloys and their fundamental properties were studied. The polycrystalline Sm3Co bulk material was prepared by the vacuum melting method. By using the polycrystalline Sm3Co bulk metal, the nanocrystalline Sm3Co alloys with an average grain size of about 8 nm was prepared by combined ball milling and spark plasma sintering. The crystal structure model was constructed and the magnetic and mechanical properties of the polycrystalline and nanocrystalline Sm3Co alloys were characterized and compared with each other in detail. Results show that the nanocrystalline alloys exhibit magnetic properties and high mechanical properties. Microhardness and elastic modulus of the nanocrystalline Sm3Co alloys are 4.87 GPa and 63.7 GPa, respectively, which are increased by 8.7% and 13.3% as compared with the polycrystalline alloys.