Concentration of oxygen vacancies, optical absorption and microstructure of Ce0.9Tb0.1O2−δmaterial under different atmospheres (O2, He and H2) and temperatures are characterized by in situ X-ray diffraction, in situ Raman spectroscopy and confocal microscopy. In this paper, we focus on how the change in optical absorption of the sample significantly affects the observed Raman information (peak intensity and the variation rule of oxygen vacancy concentration) under in situ conditions. With increasing temperature, the optical absorption of the sample decreases because of the release of oxygen and consequent changes of the microstructure. The decline in the optical absorption enables the Raman laser to increase its sampling depth, therefore, the deeper layer phonons in the structure are also sampled and contribute to the Raman scattering when the same excitation laser line is used. A more pronounced effect is observed when 514 nm laser line is used rather than 785 nm excitation, because both Tb and oxygen vacancies are enriched on the surface of the material and the 514 nm light provides surface information, while 785 nm light provides almost complete information on the sample.