The Pd/W/Si(lll) interface reaction has been investigated by XRD, XPS and AES. As the annealing temperature was low, no reaction among Pd, W and Si can be detected, but W started to diffuse into Pd and Si started to diffuse into. W. When the annealing temperature was raised, Pd and W were mixed and Pd diffused into Si substrate. When the annealing temperature was raised further, the interface reaction leads to a redistribution of the two metals with accumulation of the refractory metal at the outer layer, such a layer can be used as a diffusion barrier to protect the inner shallow contact layer.