This work indicates the synthesis of uniform core/shell nanostructures (AuR/Ag) with different thicknesses of Ag shell by the double seed method. This method consists of two self-sufficient progresses, one seed for the formation of gold nanorods (AuRs) and one for the formation of the Ag shell for the gold nanorods to form the AuR/Ag. Acid ascorbic (L-AA) acts as a weak reducing agent and hexadecyltrimethylammonium chloride (CTAC) acts as a surfactant for Ag shell. The formation and growth of the Ag shell were carefully investigated by changing the reaction factors such as temperature, time, and concentration of AgNO3. The greater the concentration of AgNO3 shelling precursor, the thicker the shell and therefore the more high-energy vibrational modes appear in the near-ultraviolet region. In survey of surface-enhanced Raman scattering effect of AuRs and AuR/Ag with Rhodamine B (RB) detector, the results show that AuR/Ag has the ability to enhance Raman signal much better than AuRs. At the same time, the thicker the Ag shell, the better the Raman signal enhancement ability.