Cu/Al bi-metal plates were produced by asymmetrical cold rolling and subsequent annealing treatments were applied to the as-rolled bi-metal plates. The effects of annealing temperature on the bond strength, locations and compositions of de-bonding failure layer development of the samples were investigated by using Instron tensile testing machine, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS). The study revealed that diffusion annealing generally did not improve the bond strength of Cu/Al bi-metal plates. The thickness of diffusion layers reached 7.31 μm when annealed at 350 ℃ for 2 hours and 15.53 μm when annealed at 500 ℃ for 2 hours. Through microstructural inspection, it was found that fractures of the as-peeled materials appeared in the Al-rich layer near the middle of the diffusion layers. Further investigations indicated that the major compositions of fracture layers were CuAl and CuAl2 phases. Brittle intermetallic phases generally determined the bond strength of Cu/Al bi-metal plates. Furthermore, bond strength was also related to the original cracks and no-bonding area formed during cold rolling. When annealing temperature fell below 350℃, Cu/Al bi-metal plates displayed relatively better bonding properties.