The diffusion processes of single adatoms Ag,Pd and Cu on Cu（001） surface are investigated by molecular dynamics. By observing the mechanisms of selfdiffusion and heterogeneous diffusion, the diffusion frequencies of three kinds of adatoms under different temperatures are counted and diffusion barriers and the preexponential factors of diffusion frequency are fitted. The results of diffusion barriers are compared with those from the static calculation. The results show that: Under 800 K, the dominant diffusion mechanism of adatom Ag,Pd and Cu is the simple hopping mechanism. The hopping frequency of adatom Ag is the biggest, and that of adatom Pd is the smallest. For homogeneous and heterogeneous adatom diffusion processes, the relationship between diffusion frequency and temperature obeys the Arrhenius formula. The diffusion barriers fitted from Arrhenius formula are relevant to the surface structure and the cohesive energy of adatom on the surface. The transition temperatures of diffusion from the jumpmechanismdominant to the exchangemechanismdominant are about 825 K and 937 K for Pd and Cu adatoms respectively.