Abstract The hardness measurement, optical microscopy (OM), and transmission electron microscopy (TEM) microstructure observation on the annealing behaviors of Cu-Al 2O 3 (2.25 vol.% and 0.54 vol.% Al 2O 3) and Cu-0.52vol.%Nb alloys were carried out. The results show that with the increase of annealing temperature, the hardness of Cu-Al 2O 3 alloys decreases slowly. No change of the fiber structure formed by cold rolling in the Cu-2.25vol.%Al 2O 3 alloy is observed even after annealing at 900°C, and the higher dislocation density can still be observed by TEM. Less combination of fiber formed by cold rolling and subgrains are observed in the Cu-0.54vol.%Al 2O 3 alloy annealed at 900°C. With the increase of annealing temperature, the hardness of the Cu-0.52vol.%Nb alloy exhibits a general decreasing trend, and its falling rate is higher than that of the Cu-Al 2O 3 alloys, indicating that its ability of resistance to softening at elevated temperature is weaker than that of the Cu-Al 2O 3 alloys. However, when annealed at a temperature of 300–400°C, probably owing to the precipitation strengthening of niobium, the hardness of the Cu-0.52vol.%Nb alloy arises slightly. The fibers formed by cold rolling become un-clear and un-straight and have less combination, and considerably more subgrains are observed by TEM.