The surface photovoltage properties of porous silicon layers were investigated as a function of anodization using surface photovoltage spectroscopy ( SPS), combined with photoluminescence spectroscopy (PL),Fourier transform IR spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the chemical composition, microscopic structure : and photovoltaic behavior of the porous silicon layers depend strongly on the anodizing conditions. It is suggested that the chemical composition and microscopic structure model the electronic and optical properties of porous silicon. The SPS and PL experiments indicate directly the excitation and emission processes of porous silicon layers. Marked differences were observed in the SPS and PL spectra of porous silicon layers with a variety of chemical compositions and microscopic structures. These experimental observations provide a clear signature of the correlation of excitation and emission in porous silicon.