Abstract: Using the ASED-MO method, the chemisorption and surface diffusion of Cu on Pt (111), (100), (110) are studied.The activation energies and the diffusion coefficients at 300K. of Cu atoms on these three Pt Surfaces are 0.167eV, 0.162eV, 0.667eV and 3.04×10¹⁰m²/s,3.69×10^-10m²/s,2.42×10^-18m²/s respectively. It is Shown that,the activation energies are rather small and Cu atomes have a high mobility on Pt (111) and (100) Surfaces;But on Pt(110),the activation energy is comparatively large and the diffusion eoefficient is small.