In this work, Bi₂MoO₆/BiFeWO₆ heterojunction was synthesized for the first time by solvothermal and calcination methods. The heterostructured Bi₂MoO₆/BiFeWO₆ exhibited higher photocatalytic oxidation/reduction efficiency than Bi₂MoO₆ for the removal of rhodamine b (RhB) dye under visible light, which was attributed to the combined effect of the n-n heterostructure and oxygen vacancies (OVs). The OVs generated by calcination can accelerate the separation of photogenerated electrons and holes. Moreover, it is also able to trap electrons to reduce the recombination of electrons and holes. In cyclic experiments, the removal efficiency was maintained above 95% after 4 times of the same operation. The effective photocatalytic mechanism of n-n heterojunctions was demonstrated by trapping experiments and EPR. The research of Bi₂MoO₆/BiFeWO₆ is beneficial to expand the advantages of bismuth-based semiconductors for environmental remediation.