Various residues containing uranium and transuranic are considered to be generated in pyroprocessing, and provided that the actinide elements are recovered from the residues, this can contribute to increasing the recovery ratio in the entire process. In this study the chemical form of the anode residues generated in our previous electrolysis test was investigated. The anode residue consisted of PuOCl, PuO2, and UO when electrolysis was performed using reduced oxide fuels, which are thought to be formed by the reaction between the anode residue and U-chloride contained in the molten salt. By adding ZrCl4 the actinide contained in the residue was converted to chloride. The chlorination reaction took [approximately]10 h to complete.