XAFS studies were performed in a study of americium sesquioxide (Am 2 O 3 ) with A-type rare earth oxide structure and americium dioxide (AmO 2 ) with fluorite structure. EXAFS results on the Am-L III absorption edge of Am 2 O 3 and AmO 2 were in good agreement with crystallographic data resulting from X-ray diffraction analysis. Theoretical assignments were performed using the all-electron Full Potential Linearized Augmented Plane Wave (FP-LAPW) method in characterizing XANES with regard to the electronic structure of Am 2 O 3 and AmO 2 . The theoretical XANES spectra of Am 2 O 3 and AmO 2 well reproduced the experimental ones. In addition, it was found that the white line peak was created due to the interaction between the Am-d and O-p components, and the broad peak and the tail peak were created due to the interaction between the Am-d and O-d components.