CF₃I, as a novel “Halon” replacement fire-extinguishing agent, has the characteristics of low fire-extinguishing concentration, high efficiency, and safety. However, there are still some gaps in its thermal decomposition studies when it is released into the high-temperature fire, so the thermal decomposition of CF₃I in oxidizing environments was studied to simulate its diffusive decomposition. The decomposition of CF₃I was demonstrated to be accelerated by O₂ through experiments in the temperature range of 100°C-800°C in air and N₂ atmosphere. The effects of initial concentration, temperature, and residence time on the decomposition rate of CF₃I and decomposition characteristics were investigated by tube furnace simulation. The kinetics of thermal decomposition was calculated using the Arrhenius equation in which activation energy E_a is 15.18 kJ/mol and pre-exponential factor (A) is 13.87s⁻¹. Additionally, the thermal decomposition products were examined by GC-MS and FTIR. The experimental results showed that the pyrolysis gas products were mainly CF₄, C₂F₆, and CF₂O. Using quantum chemistry and density flooding theory (DFT) calculations, it was concluded that the main decomposition pathway was the reaction of CF₃I with singlet oxygen. The reaction pathway of the thermal decomposition of CF₃I under a high-temperature fire oxidation environment was proposed based on the products.