Electronic structure of SmCo7- xHfx compound is calculated by using the multi-scattering X α method. It is shownthat a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co atoms.The 3d-5d coupling is stronger, which is the main reason to result in the long-range ferromagnetic order betweenSm and Co atoms in SmCo7-xHfx. According to the Stoner criterion, the result of spin-unpolarized calculationfor the Sm5Co32Hf2 cluster could lead to a better understanding of why the ferromagnetic SmCo7-xHfx is astable phase. For the Sm5Co32Hf2 cluster the Fermi level is situated at the overall maximum of the density ofstates. Moreover the cluster wavefunctions at EF are antibonding and hence highly localized in real space, whichwould lead to a large value for the cluster Stoner integral. Thus a rationalization for the magnetic stability ofSmCo7-xHfx has been obtained.