Chromite ore processing residue（COPR） is a by-product of the chromium salt processing and production industry,which contains a large amount of water-soluble and insoluble hexavalent chromium[Cr（Ⅵ）].The leaching of Cr（Ⅵ） exhibits great harm to human being and the ecological environment.A new process for detoxification treatment of COPR was developed,which included mixing and pyrolyzing COPR with the agricultural waste of citrus peel（CP） and the resulted reduction gas and biochar were used to effectively reduce Cr（Ⅵ） to trivalent chromium[Cr（Ⅲ）].Besides,the process parameters such as pyrolysis temperature,CP/COPR mass ratio,pyrolysis time,and ball milling time on the reduction efficiency（RE） and resi-dual quantity of Cr（Ⅵ） were systematically investigated.The results showed that the pyrolysis of the COPR with CP exhibited an excellent detoxification effect on COPR,and Cr（Ⅵ） could effectively be converted into trivalent chromium[Cr（Ⅲ）].The reduction efficiency of total Cr（Ⅵ） could reach as high as 99.51%.After the detoxification treatment,the total amount of Cr（Ⅵ） in the COPR decreased from 1 641.977 mg/kg to 8.04 mg/kg,which was well below the national emission standard of China of 25 mg/kg（HJ/T 301—2007“Environmental protection technical specifications for pollution treatment of the Chromi-um residue”）.Subsequently,the XRD analysis of COPR after detoxification showed that the phase compositions before and af-ter pyrolysis of COPR were identical.The research results could provide an alternative solution to the detoxification of the COPR from the lime-free roasting process of chromium salt industry.