Activation of lattice oxygen species in oxides is an important research topic for improving catalytic oxidation activity. Herein, we tuned the lattice distortion of Mn3O4 spinel oxide via interfacing with amorphous samarium oxides, which would facilitate the activation of lattice oxygen. The crystalline Mn3O4 dispersed uniformly on the amorphous SmOx with a large surface area, which builds abundant interfaces along with many active sites. The lattice distortion degree can be conveniently regulated by changing Sm amount and calcination temperature. The Sm0.3Mn (Sm/Mn molar ratio is 0.3, the calcination temperature is 400?) exhibited the optimal intrinsic ac-tivity for CO oxidation. Compared with the pristine Mn3O4, its TOFMn increased by 60%, and the reaction rate in wet conditions (10 vol% H2O) was fourfold faster, superior to most reported MnOx oxide catalysts. Integrating with the various characterizations, the improvement of the intrinsic activity fundamentally originates from the rich reactive oxygen species in the lattice-distorted Mn3O4. What's more, the Sm0.3Mn exhibited better water resistance and SO2 tolerance. Electron characteristics and characterization results revealed that the full filling of the outer shell orbits of samarium protected the active sites at the interfaces from interacting with water. The weakened capacity for SO2 oxidation decelerated the accumulation of sulfate species. This work provides new insights into the rational modulation of reactive oxygen species and developed a practical catalyst with efficient catalytic CO oxidation activity, and excellent water resistance and SO2 tolerance.