Abstract: Voloxidation is a promising headend technology in the reprocessing of spent fuel, which can not only effectively control tritium, but also simplify the subsequent process. To predict the oxidation behavior of spent fuel and provide references for the voloxidation process, the oxidation behavior of simulated spent fuel segment at 673-873 K was studied with a rotary voloxidizer. The results show that the oxidation rate and the particle size of oxidation products (less than 200 μm) increase with the temperature at 673-873 K. The conversion rate is only 86% at 823 K, because the pellets inside the claddings fail to fully react. Besides, when the temperature is below 773 K, the oxidation of simulated spent fuel segment is not sufficient. Therefore, 773 K is the optimum temperature for the voloxidation process at 673-873 K.