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Large photoinduced transmission and reflection is observed in porous silicon (PS) films in the spectral region 1.6–3.2 eV by using a femtosecond pump-supercontinuum. probe technique. The measured nonlinear transmission and reflectivity spectra have a fast component ~500 fs. The spectral structure and relaxation dynamics of the short-lived component with slowing down of relaxation rate at ~1.95 eV and ~2.5 eV are suggestive that relaxation processes correspond to nanocrystallites defects scattering. Observed coherent phonons vibrations at 518 cm-1 and 480 cm-1 may be attributed to the size of crystallites ~5 nm and due to presence of a disordered phase, respectively.