Abstract: Surface oxides structure of uraniumniobium alloys which were annealed under different temperatures (room temperature, 100, 200, 300 ℃, respectively) in air were studied by X-ray photoelectron spectroscopy (XPS) analysis and depth profile. Thickness of thermo-oxide layers enhance with the increasing oxide temperature, and obvious changes to oxides structure are observed. Under different delt temperatures, Nb₂O₅ are detected on the initial surface of U-Nb alloys, and a layer of NbO mixed with some NbO_x(02O₅ and Nb metal. Dealing samples in air from room temperature to 200 ℃, non-stoichiometric UO_2+x(UO₂ + interstitial oxygen, P-type semiconductor) are found on initial surface of U-Nb alloys, which has 0.7 eV shift to lower binding energy of U 4f_7/2 characteristics comparing to that of UO₂. Under room temperature, UO₂ are commonly detected in the oxides-layer,while under temperature of 100 and 200 ℃, some P-type UO_2+x are found in the oxide layers, which has a satellite at binding energy of 396.6 eV. When annealing at 300 ℃, higher valence oxides, such as U₃O₈ or UO_x (2f_5/2 and U 4f_7/2 peaks are 392.2 and 381.8 eV, respectively. UO₂ mixed uranium metal are the main compositions in the oxide layers. From the results, influence of temperature to oxidation of uranium is more visible than to niobium in uranium-niobium alloys.