A super hydrophobic microstructure was prepared on aluminum-alloy surface by replacement reaction with copper salt. Super hydrophobic performance was obtained by modification with low surface energy of stearic acid. The super hydrophobic surface was characterized using SEM. The result showed that there are micro-nano-structures on the surface of aluminum alloy, which has the key function for the super hydrophobic performance; the replacement method can be used to prepared aluminum-alloy surface of good super hydrophobic performance with contact angle of 161.9° and sliding angle of 4°. The surface has a broad application prospect in packaging field.