Abstract: The morphology of oxidation film has been investigated in Fe-Cr alloy contained cerium by SAM and XPS as well as SEM. The constituents of oxidation layers at different depth have been measured at intervals some nanometers and the constructs state and real-time have been analyzed. The experimental results show that chromium migrate outwards so that the composition and structure of oxidation layers change and cerium atoms diffuse and segregates on interface. The influences of trace cerium on the diffusion of alloy element chromium further have been investigated durig oxidation.