Abstract: Co/Cu/Co sandwiches were fabricated on crystalline silicon substrate by UHV electron beam evaporation. The influence of substrate orientation, material of buffer layer and fabrication temperature on the giant magnetoresistance （GMR） effect in the sandwiches was studied. By using Atomic Force Microscope, the relationship between the surface （interface） roughness and GMR effect in the sandwiches was revealed. The mechanism of the degeneration of GMR effect in the sandwiches after high temperature annealing was also analyzed.