Abstract: Z-scheme BiVO_4−x/g-C₃N_4−x heterostructure mediated by double defects were prepared by solid phase sintering and hydrothermal methods to acquire an efficient photocatalytic system for full water splitting. The microstructure and optoelectronic properties of the heterostructure were characterized, and the photocatalytic properties of BiVO_4−x/g-C₃N_4−x heterostructure for hydrogen and oxygen production by overall photocatalytic water splitting were tested. The results show that the introduction of abundant oxygen vacancy and nitrogen vacancy, the tightly connected interface and the construction of direct Z-scheme heterojunction improve the visible light absorption and accelerate the separation and transfer of photogenerated charge. As a result, the material has highly efficient photocatalytic activity. The Z-scheme BiVO_4−x/g-C₃N_4−x heterojunction mediated by double defects show excellent photocatalytic activity and stability. Under visible light irradiation, the hydrogen and oxygen evolution rate reach 654 μmol·h⁻¹·g⁻¹, which is 6.5 times as high as that of g-C₃N_4−x precursor, and the oxygen evolution rate reach 302 μmol·h⁻¹·g⁻¹. After 20 h of visible light irradiation, the photocatalytic activity of the sample doesn’t decrease.