Spherical cerium dioxide (CeO2–S) nanoparticles were successfully prepared using a solvothermal method, and their performances in catalytic oxidation reactions were studied. The CeO2–S catalyst showed superior low-temperature catalytic activity for styrene removal (T90 = 118 °C, GHSV = 18,000 h−1) compared with commercial CeO2. The characterization results showed that there were numerous oxygen defects in CeO2–S that were key to its catalytic performance at low temperatures, high redox properties, and high adsorption capacity for the reaction gases (O2 and styrene). Moreover, the catalytic performance of CeO2–S was highly stable (132 h), and the particles were reusable. FTIR and in-situ DRIFTS results showed that the type of intermediates formed during the oxidation of styrene determined the CeO2 catalytic stability, and the main intermediates were bidentate carbonate species that accumulated on the surface of deactivated CeO2–S and were not thermally stable. Moreover, the soft carbon that also deposited on CeO2–S during the reaction was easily decomposed at higher temperatures. The role of the oxygen vacancies on the CeO2–S catalyst was further revealed by correlating the concentration of oxygen vacancies and the accumulation of coke on the catalyst surface. Display omitted •Defect-rich CeO2–S shows super Low-temperature catalytic degradation of gas phase styrene (T90 = 118 °C).•CeO2–S catalyst exhibits excellent catalytic stability (132 h) and reusability.•Identify the main intermediates (carbonate) during styrene oxidation process by in-situ DRIFTS.•A quantitative correlation between the concentration of oxygen vacancy and coke accumulation is established.