Hierarchical Bi2MoO6 spheres in situ assembled by monolayer nanosheets were successfully prepared via a cetyltrimethylammonium bromide (CTAB)-assisted assembled strategy under different prepared conditions. The structure, morphology and surface chemical state of the prepared samples were well characterized. The AFM images (Atomic force microscopy) present that the average thickness of the nanosheets for two typical samples are about 0.81 and 0.84 nm, respectively. The analysis results of O 1s XPS and in-situ ESR indicate that there are different concentration oxygen vacancies (OVs) in two prepared samples (denoted as Vo-rich and Vo-poor). Time-resolved fluorescence emission decay spectra show that the carriers lifetime of Vo-rich and Vo-poor are 5.18 and 1.59 ns, respectively. Moreover, in-situ FTIR of benzyl alcohol (BA) absorption results suggest that rich oxygen vacancies could facilitate BA coordination. Vo-rich and Vo-poor present 38.2% and 7.1% of conversion with high selectivity for benzyl alcohol oxidation under visible light irradiation, respectively. The higher performance for Vo-rich was attributed to rich oxygen vacancies which act as the sites for the reactant activation. Finally, a feasible reaction mechanism was proposed to elucidate that enhanced photocatalytic activity over the Vo-rich.