The thermal annealing effects of stacking layers Mo/Si were studied by Rutherford back scattering (RBS), optical reflection, scanning electron microscopy (SEM), X-ray diffraction and X-ray reflection methods. In RBS measurement of Mo/Si system, diffusion phenomena appeared at higher annealing temperature than 400°C. In the other methods, remarkable changes were also observed in respective spectral profiles for the system annealed at the temperature higher than 500°C. The density of Mo metal film was estimated as 80% or more of bulk material.