AlH3 is a high-capacity hydrogen storage material but is prone to explosion. Thermodynamic and structural properties of AlH3-nanoparticles at different CO2 inerting systems from ignition to combustion are studied using ReaxFF-MD method. The influence of CO2 on AlH3-nanoparticles ignition and combustion is investigated by comparing the changes of surface O adsorption rates, particle charge, temperature rise rates and so on. Results indicate that an increase in CO2 is crucial for suppressing AlH3-nanoparticles ignition and combustion by impeding the formation of an Al-rich environment. In contrast to three stages of AlH3-nanoparticles combustion in pure O2 system: surface combustion, slow temperature rise, and self-sustaining combustion, the process of CO2 inerting system is different, with third stage is slow temperature rise at a constant rate. When CO2 concentration reaches to 90%, the dehydrogenation rate reduces by 70.0%, the temperature rise rate decreases by 78.6%, and the ignition delay time reaches 45 ps.