The influence of the different buffer layers on the giant magnetoresistance (GMR) of the Co/Cu/Co sandwich was investigated. It was found that the GMR effect strongly depends on the magnetism of the buffer layer and crystallization of the sandwich induced by the buffer layer. Due to the anti-ferromagnetic coupling between the Cr and Co layer, anti-ferromagnetic Cr layer enlarged the difference of the magnetic behavior between the two Co layers and presented a high GMR value larger than 6%. However, as the coercive force was enlarged also, its magnetic sensitivity could not be high. Ti and Ni buffer layer could form strong (111) texture in the sandwich, which also enlarged the difference between the two Co layers, and achieved GMR values over 5%. Furthermore, the ferromagnetic Ni layer reduced the coercive of the sandwich, and enhanced the sensitivity significantly.