Thermodynamic oxygen isotope factors for uranium oxides have been calculated by means of the modified increment method. The sequence of ¹⁸O-enrichment in the uranium oxides with respect to the common rock-forming minerals is predicted as follows: spinel < uraninite ≤ brannerite ≤ hematite < rutile < pitchblende < cassiterite ≤ uranium blacks ≤ coffinite < sedovite ≤ UO₃ < illite. Two sets of self-consistent fractionation factors between the uranium oxides and water and between the uranium oxides and the other minerals have been obtained for 0~ 1200°C. The theoretical results are applicable to the isotopic geothermometry of uranium ores when pairing with other gangue minerals in hydrothermal uranium deposits.