In this study, yttrium-doped CeO2 with a broom-like porous hierarchical structure was successfully prepared by a simple template-free hydrothermal method with cerium nitrate hexahydrate and yttrium nitrate hexahydrate as original materials. Through systematic experiments, the different effects of doping concentrations on characteristics of the ceria were examined in detail and the optimal doping ratio was determined simultaneously. The morphology and element distribution of the as-prepared samples were characterized by field emission scanning electron microscopy and high-resolution transmission electron microscopy. Structure information with Rietveld refined data were obtained by using an X-ray diffractometer. Extinctive oxygen vacancy and doping oxygen vacancy were analyzed from Raman spectra. Analyses of elements and chemical valence analysis were carried out by X-ray photoelectron spectroscopy, and changes in reactive oxygen species were determined by calculation. Based on structural information, element valence states, results of hydrogen temperature-programmed reduction and oxygen temperature-programmed decomposition analysis and the results of photocatalytic decomposition of acetaldehyde, we can draw the conclusion that a certain amount of Y-doped CeO2 with a broom-like porous hierarchical structure has high catalytic activity, attributed to more oxygen vacancies and surface active oxygen species generated after yttrium doping.