A simple, low-cost, and high-efficient method is used for the fabrication of surface-enhanced Raman scattering (SERS) substrates. Silver particles deposited on porous silicon are prepared as a highly efficient SERS substrate by direct immersion of porous silicon in silver solution. The SERS measured with rhodamine 6G as a target molecule is affected by the morphology of silver particles on the top of porous silicon layer. The effect of solution concentration, dipping time, and thickness of porous layer on the morphology of silver particle is investigated. Highly efficient SERS spectra are observed for substrates with porous layer thickness of about 3 μm and incubated in the 50 mM AgNO3 solution for 3 minutes. The SEM images of the substrates show that there are many small Ag particles with the size of a few nanometers among large Ag particles with the size of several microns.