Abstract: BiOCl, BiOBr and BiOI were prepared by hydrothermal and solvothermal methods. XRD, SEM, photocurrent density curve and UV-vis were used to characterize the crystal structure, surface morphology and photoelectric properties. The band structure and density of states of BiOX were calculated by DFT. With the atomic number of halogen increase, the dispersion of the Fermi level near the semiconductor conduction band decreases, and the band gap becomes smaller. The photocatalytic activity of BiOCl, BiOBr and BiOI was evaluated by photocatalytic degradation of Rhodamine B (RhB), and the degradation rate of RhB in 60 min for BiOI could reach 100%. Meanwhile, the main active groups in the process of photocatalytic degradation of RhB were explored by radical trapping experiment.