Defect-mediated Z-scheme BiO2-x/Bi2O2.75 heterojunction photocatalysts without electron mediator was prepared via a simple low-temperature hydrothermal method. DFT proved that the existence of oxygen vacancies would affect the geometric and electronic structure of BiO2-x and Bi2O2.75, which played an indispensable role in promoting exciton dissociation. BiO2-x/Bi(2)O(2.75 )exhibited a higher redox ability compared with the pure BiO2-x due to the Z-scheme photocatalytic mechanism, which could be ascribed to the formation of the build-in electric field induced by Bi and O defects. The as-synthesized photocatalysts exhibited excellent photocatalytic activity over the full solar spectrum from UV to NIR light due to the LSPR effect of oxygen vacancies, indicating its effective utilization of solar energy. The degradation rates of RhB over the optimal BiO2-x/Bi2O2.75. were 8.49, 10.22 and 3.24 times higher than that of the pure BiO2-x under visible light, simulated sunlight and NIR light irradiation, respectively. The excellent photocatalytic activity was ascribed to the synergistic effects of the LSPR effect of oxygen vacancies and the Z-scheme interfacial heterojunction. It was believed that this work provided a new idea to design high active and full solar spectrum-driven photocatalysts for energy conversion and environmental remediation.