The microstructure and texture evolution of Cu-Nb nanocomposite wire after heat treatment were characterized by the scanning electron microscope and electron backscatter diffractometer (EBSD). The recrystallization, nucleation, large angle boundary, and residual internal stress of the nanocomposite were also discussed. Results demonstrate that after the annealing treatment, the grain recovery and recrystallization occurs in the Cu-Nb nanocomposite and a small number of large angle boundaries appear. The residual internal stress becomes weaker after the annealing treatment. After annealing over 600 °C, the grains in Nb filaments are recrystallized and grow significantly. The Cu-Nb nanocomposite wire has good structural stability at high temperatures.