Defect engineering can offer active sites for N2adsorption and activation due to the abundant localized electrons of surface defects. However, the high energy barriers of the defect band can restrict the electron transfer, which thus limits the photocatalytic N2fixation performance. Herein, we demonstrate that Ru/W18O49exhibits a nearly 6-fold enhanced photocatalytic activity for ammonia production under visible irradiation compared with pristine W18O49. Our investigations reveal that the enhanced photocatalytic N2fixation activities are mainly attributed to the synergistic effect of oxygen vacancies and Ru modification. The decorated Ru species can modify the coordination structure of oxygen vacancies by forming Ru–O–W bonds. The Ru–O–W centers can serve as active sites for the side-on adsorption of N2due to their asymmetric polarization, better promoting the electron transfer to absorbed N2. Moreover, the LSPR between Ru and oxygen vacancies provides sufficient electrons for N2activation. As a result, the efficient electron transfer facilitates the activation and dissociation of N2on Ru/W18O49, which is feasible for the reduction of N2to NH3. This work provides a promising strategy for enhanced photocatalytic N2fixation by modulating defect engineering.