Abstract: Fluoride volatility method is regarded as a promising advanced pyrochemical reprocessing technology, which can be used for separation and recovery of uranium from spent fuel. The fluorination of UF₄ by F₂ to produce UF₆ in KF-ZrF₄(x=42%-58%, FKZr) has been investigated. In this study, the Fourier transform infrared spectroscopy(FTIR) was used for in-situ monitoring of fluorination process. The product of fluorination, UF₆, was collected by the multi-stage condensation. After the fluorination, the uranium mass fraction in the molten salt is below 2.5×10-3%, the UF₄ conversion rate is higher than 99.9% and the product recovery is above 90%. The results show that the fluorination process, and the in-situ monitoring of process by FTIR are feasible. In addition, the study also show that the fluorination has high decontamination efficiency for UF₆ product, and the decontamination factors for alkali metals and rare earth elements are 103 to 105.