Abstract：Using calcined sulfate-modified titanium-bearing blast furnace slag as photocatalyst, the photocatalytic reduction of Cr(VI) in Cr(VI)-acetic acid (AA) compound system was studied. The effects of initial pH value, concentration of Cr(VI), AA/Cr(VI) volume ratio, synergistic effect factor and reuse on its photocatalytic reaction performance were also investigated. The results indicate that with increase of AA/Cr(VI) volume ratio up to 0.2%, the reduction efficiency of Cr(VI) significantly increases up to 27.55%, and thereafter it decreases gradually. The acidic solutions are favorable for the photocatalytic reduction of Cr(VI), and the optimum pH for the reduction of Cr(VI) is 1.5. Under the same conditions of 110 min and pH 1.5, the photocatalytic reduction efficiency of Cr(VI) is 76.32% for single Cr(VI) system and 100% for Cr(VI)-AA system. Cr(VI) is more efficiently eliminated in Cr(VI)-AA compound system than in single Cr(VI) system, and the synergistic effect factor is always greater than 0, indicating that there exists a synergistic effect in the compound system. The photocatalytic reduction of Cr(VI) in Cr(VI)-AA system follows Langmuir-Hinshelwood kinetic model.