A novel Co3O4/Bi12O17Cl2 heterojunction catalyst has been constructed for the first time via a sample hydrothermal course. The chemical, optical and physical properties of as-constructed materials were examined by XRD, XPS, TEM, and DRS methods. These results demonstrated that Co(3)O(4 )nanoparticles evenly dispersed on Bi12O17Cl2 flakes, forming heterojunction nanostructure. When Co3O4/Bi12O17Cl2 photocatalyst was used for degrading rhodamine b (RhB), the best Co3O4/Bi12O17Cl2 sample (0.122 min(-1)) exhibited 2.5 folds higher rate constant than bare Bi12O17Cl2 (0.048 min(-1)), which owed to the collaborative interactions of heterojunction between Co3O4 and Bi12O17Cl2, accelerating validly the separation of photo-generated carriers, boosting visible light absorbance. Simultaneously, various radical scavenger tests indicated that center dot O-2(-) and h(+) were prime parts for heightening activity. Eventually, depending on the above experimental conclusions, a photocatalytic mechanism was presented for the Co3O4/Bi12O17Cl2 heterojunction.