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The interface chemical reactions, the deoxygenation and the overall thermal stability of the ex situ deposited graphene oxide (GO) thick film on the polycrystalline tantalum surface were studied by means of x-ray photoelectron spectroscopy (XPS) at room temperature and after annealing up to 600 °С. The evolution of the Ta4f, C1s and O1s XPS core level spectra from the Ta/GO structure under study upon the increase of the annealing temperature was investigated with the reference to the uncovered Ta substrate surface. In the Ta/GO structure the Ta relative atomic concentration was about 1% at room temperature due to the low porosity of the GO layer while the thermal desorption of the overlayer at the elevated temperatures was accompanied by an increase of the Ta concentration up to 47% at 500 °С. The C atoms relative concentration started decreasing after the annealing at 250 °С accompanying the thermal desorption of the GO overlayer. The formation of the TaC compound starting from the 250 °С annealing temperatures was determined. The relative oxygen concentration in the GO thick film was decreased upon increasing the annealing temperature accompanying both the thermal desorption of the GO material and the thermal reduction of the GO film. Keywords: Graphene oxide, Tantalum oxide, Surfaces and interfaces, Thermal treatment, X-ray photoelectron spectroscopy