Silver nanoparticles are of great interest in the past decade due to their unique physical and chemical properties different from bulk materials. Such particles have been used in the development of many important applications. In our work, silver nanodecahedra and nanoprisms are synthesized upon LEDs irradiation by simply adjusting the wavelength and temperature. The products are characterized by UV-vis spectra and transmission electron microscopy (TEM). Surface-enhanced Raman scattering (SERS) can be modulated through varying the morphology and size of silver nanostructures. The enhancement effects were investigated using Rhodamin 6G (R6G) and crystal violet (CV) as probe molecules at various laser excitation wavelengths of 514, 633, and 785 nm. The results show that the enhancement effect of SERS can be modulated by the coupling effect between the localized surface plasmon resonance of nanoparticles and the laser excitation wavelength. This work will be of significance in understanding the SERS enhancement mechanism and in the fabrication of silver nanoparticles-based devices for biosensing.