The influences of reaction parameters, including pyrolysis temperature, reaction time and the mass ratio of PE/COPR, on Cr (VI) reduction were evaluated. The change of chromium speciation during the treatment was studied by XANES and EXAFS spectroscopy. The results indicated that, (1) Through the co-pyrolysis treatment, the Cr (VI) reduction can be effectively reduced. When the temperature reaches 550℃, the reduction rate could reached to 99.93%. The Cr (VI) reduction rate gradually increased with the rising dose of PE and then became stable when the mass ratio was over 0.05. Cr (VI) reduction rate rapidly increased during the initial reaction time while almost unchanged after 6min. The optimum reaction condition was evaluated as below: pyrolysis temperature: 550℃, pyrolysis time: 6min, and PE/COPR: 0.05. (2) Cr₂O₃ as the reference material of Cr(III) is more accurate and reasonable than CrCl₃ during the Cr(VI) detection by XANES, and the Cr(VI) in the COPR was reduced as amorphous Cr₂O₃. (3) Compared to the biomass, PE as the reducing agent can be more efficient in Cr(VI) reduction, ascribed to the higher content of C, H and no O. (4) Cr(VI) can be continuously reduced under continuous contact with the volatile compounds generated from the pyrolysis of PE.