The detailed photoluminescence (PL), Raman and infrared absorption spectra of porous silicon (PS) prepared at different anodization current densities, annealing conditions and light illumination durations are studied. The intricate spectra imply diverse mechanisms to address the origin. We suggest that the quantum confinement effect of PS determines the blue-shift of the spectra, and that the breaking of Si-H-x bonds on the porous walls degrades the PL intensity.