Two Sm@C-82 isomers have been Well Characterized for the first time by means of C-13 NMR Spectroscopy, and their structures were unambiguously determined as Sm@C-2v(9)-C-82 and Sm@C-3v(7)-C-82, respectively. A combined study of single crystal X-ray diffraction and theoretical calculations Suggest that in Sm@C-2v(9)-C-82 the preferred Sm2+ ion position shall be located in a region slightly off the C-2 axis of C-2v(9)-C-82. Moreover, the electrochemical surveys on these Sm@C-82 isomers reveal that their redox activities are mainly determined by the properties of their carbon cages.