Revealing the role of engineered surface oxygen vacancies in the catalytic degradation of volatile organic compounds (VOCs) is of importance for the development of highly efficient catalysts. However, because of various structures of VOC molecules, the role of surface oxygen vacancies in different catalytic reactions remains ambiguous. Herein, a defective Pt/TiO2-x catalyst is proposed to uncover the different catalytic mechanisms of C3H6 and C3H8 combustion via experiments and theoretical calculations. The electron transfer, originated from the oxygen vacancy, facilitates the formation of reduced Pt-0 species and simultaneously interfacial chemisorbed O-2, thus promoting the C3H6 combustion via efficient C=C cleavage. The reduced Pt nanoparticles facilitate the robust chemisorption of bridging dimer O-2(2-) (Pt-O-O-Ti) species. This chemisorbed oxygen inhibits the C3H8 combustion by depressing C3H8 adsorption. This work offers insights for the rational design of highly efficient catalysts for activating the C=C bond in alkene or CH bond in alkane.