The electronic and lattice properties of Si and Te doped CoSb3 under hydrostatic compression conditions are calculated by using the first-principles method. Calculated compositions of Si and Te doped CoSb3 are Co8Sb24 (as the same of no doped CoSb3 [Skutterudite]), Co8Sb22Si2, Co8Sb21Si1Te2, and Co8Sb21Si2Te1. We obtain their electronic and lattice properties under high pressure (P = 100 GPa) and ambient pressure (P = 0 GPa) using the total energy pseudopotential method based on the local density approximation (LDA) [1]. The densities of state (DOS) of Si and Te doped CoSb3 under P = 0 and 100 GPa are investigated in order to compare with each other. Their DOS shapes and positions of the Fermi level vary under pressure. In particular, the variation from P = 0 to 100 GPa in Co8Sb21Si2Te1 is