Bi2O3/BiOCl composite photocatalysts were produced by a facile two step method, including ultrasonically modifying BiOCl nanosheets with Bi nanoparticles first and the subsequent in situ thermal oxidation process. The samples were characterized by XRD, SEM, UV-vis and photoluminescence techniques. The photocatalytic activities were evaluated by photodegrading Rhodamine B under Xe light irradiation. The abilities of generating hydroxyl radicals during photocatalysis were tested by fluorescence method. The results show that Bi2O3 NPs were randomly distributed on the surface of BiOCl nanosheets. The photocatalytic efficiency was enhanced after modification and the best photocatalytic activity was obtained when the mole ratio of Bi2O3 to BiOCl was 0.24. The corresponding photochemical reaction rate of Bi2O3/BiOCl was 7 times that of BiOCl nanosheets and 5 times that of Bi2O3 nanoparticles. The improved performance of the composites was considered to associate with the extended light response range and the promoted charge carrier separation.