BiOBr/Bi2Sn2O7 heterojunction photocatalysts were successfully synthesized by treating hydrothermal as-prepared Bi2Sn2O7 nanoparticles with hydrobromic acid (HBr). Partial Bi2Sn2O7 nanoparticles reacted with HBr to form the sheet-like BiOBr, and Bi2Sn2O7 nanoparticles distributed evenly on BiOBr sheets. BiOBr/Bi2Sn2O7 photocatalysts treated with different concentrations of HBr solution were successfully obtained, and their structures, morphologies, optical, and visible light photocatalytic properties were characterized by XRD, DRS, PL, SEM, and TEM. The experimental results showed that the BiOBr/Bi2Sn2O7 photocatalysts showed improved photocatalytic activity under visible light irradiation than pure Bi2Sn2O7. The sample treated with 0.08 mol/L HBr solution shows the best visible light photodegradation performance of rhodamine B. In addition, the active species and photocatalytic mechanism were discussed in detail.