Photocatalytic degradation of the azo dye orange II using NdVO4/V2O5/BiVO4 under visible light is reported here, and this oxygen-rich defect three-phase heterojunction structure is constructed using a two-step cation exchange method. This heterojunction significantly enhances the separation and migration efficiency of photo-induced charges, while the accompanying oxygen defects effectively capture photogenerated electrons, thereby suppressing the recombination of electrons and holes. Experimental characterization and theoretical calculations demonstrate the efficient separation and transfer capabilities of photogenerated carriers and their excellent photocatalytic degradation performance. Particularly, when treating the anionic dye orange II, this heterojunction structure achieves a degradation efficiency of up to 96.15%. Cycling tests show that NVB-24 exhibits good stability during the reaction process. This research provides a promising photocatalyst for the efficient degradation of anionic azo dyes and offers new insights for developing high-quality photocatalytic materials.