A series test of the pyroprocess was carried out to recover U-Pu alloy from mixed oxide (MOX) pellets. In the Li-reduction step, the reduction behavior of MOX was similar to that of UO2. In the electrorefining step, the separation factor between U and Pu was 1.9 for the combination of the reduced MOX anode and the liquid cadmium cathode, which agrees well with the value obtained in previous studies. Approximately 99% of the HM (U and Pu) initially present in the anode or molten salt was detected in the electrodes or molten salt after the electrolysis. Considering the analytical error of inductively coupled plasma-atomic emission spectroscopy, this mass balance is reasonable. The amount of U remaining in the anode was slightly larger than that of Pu, due to the reoxidation. The U-Pu alloy ingot was successfully formed by distillation of Cd.