To address the application potential and demand of propellant/supercritical carbon dioxide （SC-CO₂） in ejection work， thermal analysis， static combustion and closed combustion tests were carried out in comparison with a N₂ environment， to investigate the thermal decomposition and combustion characteristics of single-based propellant in CO₂. The results show that the CO₂ atmosphere significantly suppresses the pyrolysis process of single-based propellant， and its maximum activation energy is 15.53 kJ·mol^-1 higher than that in N₂ atmosphere. The combustion time of single-based propellant in CO₂ is remarkably prolonged， increasing by 1729 ms at 7 MPa compared with the N₂ environment. Moreover， the combustion flame of single-based propellant in SC-CO₂ exhibits a special morphology with an inner white core and outer pale red periphery. During closed combustion， the phase change and heat absorption of liquid CO₂ lead to an ignition delay of single-based propellant up to 12.20 ms， and the action duration of single-based propellant in SC-CO₂ is on the order of 10^-2 s. Increasing the initial pressure helps to improve the energy release rate of single-based propellant in the SC-CO₂ environment.