Double-atom filled single-phase CamCenFexCo4-xSb12 compounds were synthesized through a melting—quenching—diffusion—annealing procedure. Ca and Ce were used as filling atoms. The structure of double-atom filled skutterudite compounds was investigated via Rietveld refinement and X-ray photoelectron spectroscopy analysis. The results of Rietveld refinement indicate that CamCenFexCo4-xSb12 compounds have skutterudite structure, and the Sb-icosahedron voids were filled with Ca or Ce. The thermal parameter (B) of Ca/Ce is much larger than those of Sb and Fe/Co in the compounds. The specific chemical states of atoms were obtained from X-ray photoelectron spectroscopy quantitative analysis, the results show that the Sb atoms have five chemical states, and the relative percentages of Sb atoms in different chemical states are correlative with the total filling fraction. The filling atoms tend to be located at the center of the voids of the Sb-icosahedrons preferentially.