Silver nanocubes were synthesized by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) based on the report by Xia's group. Silver nanocubes were immobilized on silicon wafers by self-assembly processes. SERS activity of silver nanocubes was detected by using pyridine and SCN- respectively as probe molecules. The preliminary results show that the Raman intensities of pyridine and SCN- adsorbed at silver nanocubes were enhanced considerably, indicating that silver nanocubes can be used as a good SERS substrate. On the other hand, SERS combined with the probe molecule method can be used to characterize the optical property of silver nanocubes.