BiOCl0.5Br0.5 nanoparticles have been prepared by solid phase reaction method in a humid environment with varying contents of Bi(NO3)3.5H2O, KCl and KBr with the initial mol ratio 1.0: 0.5:0.5. X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), Raman spectroscopy, and UV-Vis DRS were used to analyze the properties of materials, including theirmorphology, crystal structure, and element distribution. Meanwhile, the XRD plot of the sample BiOCl0.5Br0.5 shows that the diffraction peaks are slightly shifted towards a wider 2 angle than that of BiOBr. This is explained by the deformation of the crystal structure when chloride is involved in the lattice, which is beneficial for the efficient generation and separation of electron-hole pairs. In addition, we evaluated the photocatalytic activity of BiOCl0.5Br0.5 on the degradation of phenol under visible light irradiation and found that the composite material (conversion of 99.11%) exhibited a higher photocatalytic activity than single BiOCl (conversion of 11,39%) and BiOBr (conversion of 24.02%) after 90 minutes of illumination.