Bi4Ti3O12/BiOBr composite photocatalyst was prepared by one step solvothermal method. The composition, morphology and photocatalytic property of the sample were determined by X-ray diffraction, scanning electron microscopy, specific surface area aperture analyzer and ultraviolet-visible diffuse reflectance spectrometer. The influence of synthesis conditions on photocatalytic activity of sample was discussed. The active species and reaction mechanism in the process of photocatalytic reaction were explored. The results show that the as-prepared sample has high photocatalytic activity and good cycling stability while the ratio of Bi, Ti, Br is 10∶7∶5, ethylene glycol is used as solvent, polyvinylpyrrolidone is used as surfactant and its additive amount is 0.2 g. After 140 min of irradiation by 7 W LED lamp, the degradation rate of photocatalyst reaches 85.1%. ?O-2 and h+play a major role in the degradation process.