The chemisorption of Ce, Sm and Yb on Si(lll) surface are studied by calculation with local density formalism (LDF) and discrete variational method (DVM). Two different clusters are used to simulate the top site and 3-fold site. The calculation is carried out self-con-sistently and the binding energy of the cluster is obtained. Optimum geometry is determined by minimizing the total energy. Charge transfer between rare earth atom and the silicon substrate, the energy of chemisorption and the density of states are discussed and compared with experimental results available.