A highly ordered anodic aluminum oxide template was prepared, the mixture of phosphate and chromic acid was used to remove the oxide layer, regular pits array on the surface of the aluminum was obtained, then AC electrodeposit method was used to get fluffy nano silver structure, which was tested with SEM. Melamine was chosen as the probe molecule, the Raman peaks of melamine with 10-12 g·mL-1 were successfully detected, and the molecule number of the melamine is about 3.8×10-6 at this concentration and laser spot through calculation, which is beyond the detection level of monolayer. The enhancement factor reached 1.41×1011.