Abstract: The dynamics of the thermal chemical reactions of UF₄ in oxygen or hydrated (relative humidity of 93%) oxygen environments were studied by micro-laser Raman spectroscopy (MLRS), gravimetry and topology techniques. The variabilities about mass and color of UF₄ were obtained at different temperatures and time, and the Raman spectra were also obtained for the reactants and the products. In both conditions, UF₄ is stable at 200 ℃ with nearly no changes in its Raman spectra. However the Raman spectra suggest the formation of UO₂F₂, UO₂ and U₃O₈ in oxygen and UO₂F₂, UO₂F₂•2H₂O, UO₂F₂•nH₂O, UO₂ and U₃O₈ in the hydrated oxygen at 250-600 ℃. On the other hand, the chemical reaction rate of UF₄ in oxygen shows the trend from slow to fast and then to slow.