Synthesis of high-efficiency photocatalysts and revealing the photocatalytic mechanism are of far-reaching significance for its commercial applications. Therefore, we design and favorably fabricate the carbonate intercalated Bi2WO6 with oxygen vacancies via employing a mild hydrothermal method with ethylene glycol assist. The prepared catalysts exhibit an excellent photocatalytic NO oxidation activity under visible light irradiation, attributing to the inserted carbonate coupled with oxygen vacancies. Additionally, the promotion mechanism and reaction pathway of photocatalytic NO removal are carefully discussed by experimental detection assisted with density functional theory (DFT) calculation. Our results explicitly reveal that the carbonate coupled with oxygen vacancies can remarkably retard the recombination of electro-hole pairs, and improve the carriers transforming to activity species. The reactants would be easily activated and converted over the carbonate-intercalated defective Bi2WO6 surface, such as the H2O provided electrons to form (OH)-O-center dot and O-2 accepted electrons to generate O-center dot(2)-, which are certified by utilizing DFT simulation to calculate adsorption of reactants on the surface. In addition, the in situ DRIFTS spectra was used to dynamic analyze the photocatalytic NO oxidation process and reveal the promotion mechanism. Finally, the synthesis strategy and mechanism analysis would possess guiding significance for improving photocatalytic efficiency and applications.