Abstract: The heated oxidation film of U-Nb alloy is studied by auger electron spectroscopy (AES) at different temperature in the high vacuum chamber. When temperature is above 603 K, the surface structure of U-Nb alloy will change greatly, and the surface is made up of UC_(x)O_(y) phase, metallic U and Nb. The heated oxidation film of U-Nb alloy is sputtered with Ar~+, and chemical compositions of the oxidation film of U-Nb alloy are studied. It shows that oxygen content is low on the surface of the heated oxidation film U-Nb alloy and high inside the heated oxidation film of U-Nb alloy.