Abstract: Bulk nanocrystalline copper with a thinkness of about 600 μm was prepared by electrodeposition, and then was annealed at 100-250℃. The effect of the annealing temperature on the microstructure and mechanical properties of the nanocrystalline copper was studied. The results show that both unannealed and annealed nanocrystalline copper showed a face-centered cubic structure. As the annealing temperature rose from 100℃ to 250℃, the diffraction peak intensity of (200) crystal faces of the nanocrystalline copper gradually increased. With the increase of annealing temperature, the tensile strength of the nanocrystalline copper gradually decreased while the elongation after fracture increased first and then decreased; and the numbers of both the surface tensile deformation zones and the large and deep dimples on the tensile fracture increased. The nanocrystalline copper had the relatively good tensile properties after annealing at 200℃, with the tensile strength up to about 500 MPa and the elongation after fracture of nearly 30.5%.