Flake　BiOBr　was　first　prepared　by　a　solution　method　at　room　temperature.　Then,　the　produced　BiOBr　was　calcined　at　different　temperatures.　It　was　found　that　BiOBr　is　not　a　stable　compound.　It　transforms　to　plate-like　Bi24O31Br11at　around　750　degrees　C　and　the　formed　Bi24O31Br11　can　further　convert　to　rod-like　a-Bi2O3　at　around　850　degrees　C.　The　prepared　compounds　were　characterized　with　X-ray　diffraction　(XRD),　N2　physical　adsorption,　scanning　electron　microscopy　(SEM),　and　UV-Vis　diffuse　reflectance　spectra　(DRS),　respectively.　The　photocatalytic　activity　of　the　produced　bismuth　oxybromides　was　evaluated　by　photocatalytic　decomposition　of　acid　orange　II　under　both　visible　light　(＞420　nm)　and　UV　light　(=365　nm)　irradiation.　Results　show　that　these　compounds　have　different　band　gaps　and　different　photocatalytic　properties.　The　band　gap　energies　of　the　as-prepared　samples　were　found　to　be　2.82,　2.79,　2.60　and　3.15　eV　for　BiOBr,　BiOBr/Bi24O31Br,　Bi24O31Br,　and　a-Bi2O3,　respectively.　Under　both　UV　light　and　visible　light　irradiation,　the　photocatalytic　activity　follows　the　order:　BiOBr/Bi24O31Br　mixture＞BiOBr＞Bi24O31Br＞a-Bi2O3.　The　change　in　photocatalytic　activity　could　be　attributed　to　the　different　light　absorption　ability　and　microstructures　of　the　photocatalysts.