The corrosion resistance of Al-Cu-Mg-Ag alloy was studied by intergranular corrosion test and exfoliation corrosion test. The mechanism was discussed by metallographic analysis and transmission electron microscopy. The results show that,the corrosion resistance of the alloy can be enhanced by appropriate rolling deformation. With increasing the deformation amount,the strengthening phases deform and move to the grain boundaries,which leads to a narrower precipitation free zone (PFZ). The corrosion channel narrows and the corrosion resistance of the alloy increase. On the other hand,the elongaged grains along the rolling direction can decrease the exfoliation resistance of the alloy. As a result,the corrosion resistance of the alloy with a relative smaller deformation amount (10~50%) is increased,and that of the alloy with a larger deformation amount (80%) is decreased.