High efficient photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over microcrystalline SrBi 2Nb 2O 9 was observed upon purging with N 2 under UV-light irradiation. Its photocatalytic activity was higher than that of sample P25 (commercial TiO 2, Degussa Co.). The analysis results of X-ray diffraction and X-ray photoelectron spectroscopy revealed that microcrystalline SrBi 2Nb 2O 9 had high stability for the photocatalytic reduction of 4-nitroaniline. Further experiments indicated that ammonium oxalate was indispensable for the photocatalytic reduction of 4-nitroaniline. Moreover, the high efficient photocatalytic reduction of 4-nitroaniline over microcrystalline SrBi 2Nb 2O 9 might be ascribed to its relatively high conduction band. Display omitted ► Photocatalytic reduction of 4-nitroaniline over SrBi 2Nb 2O 9 microcrystal was observed. ► Its photocatalytic activity was higher than that of commercial TiO 2 under UV light. ► The higher catalytic activity was attributed to its relatively high conduction band.