It is widely known that CoAl 2 O 4 , IV (Co 12x Al x ) VI [Co x Al 22x ]O 4 , is a largely normal spinel Γ°0 , x , 2=3Γ; but this cation distribution cannot be explained by the effects of cation size, electronegativity and ligand-field of Co 2ΓΎ . To examine the reason for this peculiar cation distribution, the relationship between the inversion parameters Γ°xΓ and the interatomic distances was investigated using the Rietveld analysis of X-ray diffraction. On the basis of the results of the structure refinements by Rietveld analysis, the regression equations for the mean bond lengths and Oβ’ β’ β’O distances as a function of x were calculated by a linear least-squares method. The variations of local bond lengths versus x were inferred from the regression equations for the mean bond lengths. With increasing x; the ratio (Oβ’ β’ β’O) shared /(Oβ’ β’ β’O) unshared in VI B-site octahedron increases remarkably and the local bonds on IV A-site are inferred to be abnormally lengthened. These results imply that if CoAl 2 O 4 were a largely inverse spinel, the local bond lengths on IV A-site would become abnormally long and the repulsion between VI B-site cations would become considerably large. Such destabilization factors of the crystal structure can be avoided by the largely normal configuration of cations.