The reaction sensitivity analyses were performed for determining which kinetic reaction plays an important role in the absorption process of CO2 capture using aqueous ammonia in a packed column. The operating conditions in the current typical CO2 capture processes were considered. For the temperature range of 8–48°C, NH3 concentration range of 1.0–9.0mol/L, and CO2 loading range of 0.13–0.53 of the lean solvent, the reaction of CO2 with NH3 for producing carbamate plays an important role in most conditions, but its important role is weakened with the absorbent temperature and CO2 loading increasing or the NH3 concentration decreasing. At the high temperature of 48°C and low NH3 concentration of 1.0mol/L, the reaction of CO2 with OH− for producing bicarbonate plays a more important role than the reaction of CO2 with NH3 for producing carbamate. At the high CO2 loading of 0.33, the decomposition reaction of carbamate plays a same important role as the reaction of CO2 with NH3 for producing carbamate. The reaction sensitivity analysis results can provide technical guidance for increasing the CO2 absorption rate.