Abstract: Three kinds of BiOBr crystal micropowders with different morphological structure have been synthesized via an ethylene glycol solvothermal route using the methylimidazolium bromide type ionic liquids[C₄mim]Br,[C₈mim]Br and[C₁₂mim]Br as bromo source and soft template.The results from X-ray diffraction (XRD),scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis show that the as-prepared BiOBr products all belong to tetragonal phase in high purity.The BiOBr crystals along (110) lattice plane preferentially grow with the increase of carbon atom number (C_n) of substituent group in ionic liquid cation.The micro sized BiOBr particles clusters are all consisted of nanosize petal-like flakes via self-assembly,which show radial pattern from spherical center.As the C_n number increases,the particle size and surface pores all decrease,but the specific surface area increases.The three BiOBr powders possess different catalytic activity for visible photocatalytic degradation of aniline.The degradation ratios of the aniline solution are 54.13%,78.67% and 95.06% in 280 minutes,respectively.The photogenerated holes should be the main active species in the photodegradation process,but the hydroxyl radical just plays a minor role.