Pr-doped CeO₂ with different doping levels was prepared from Ce(NO₃)₃∙6H₂O and Pr(NO₃)₃∙6H₂O by solvothermal method without any additional reagents, in which the mixed solution of ethylene glycol and distilled water was employed as a solvent. The influences of Pr-doping on phase composition, crystal structure and morphology were investigated, as well as Pr valence and oxygen vacancy defects. The Pr cations entered into the CeO₂ crystal lattice with normal trivalence and formed a Pr-CeO₂ solid solution based on the fluorite structure. The larger trivalent Pr was substituted for tetravalent Ce in the CeO₂ crystal and compensated by oxygen vacancy defects, which caused the local lattice expansion of the crystal lattice. Moreover, the Pr-doped CeO₂ solid solutions exhibited visible color variation from bright cream via brick red to dark brown with the increasing of Pr contents. The degradation of AO7 dye was also investigated using a domestic medical ultraviolet lamp; the removal efficiency of AO7 by 1% and 2% Pr-doped CeO₂ approached 100%, much higher than 66.2% for undoped CeO₂.