The transient behavior of liquid droplets was crucial for enhancing the thermal performance of the horizontal falling film CO₂ absorbers. A two-dimensional mathematical model of the droplet model flow falling film absorbing CO₂ was established based on the volume of fluid（VOF）method. The effects of the Reynolds number Re and the tube spacing on the droplet pulsation in the process of the falling film absorbing CO₂ were analyzed by introducing the drop length and the dimensionless time. The results showed that in the period of the formation for liquid droplets at the bottom of tubes, affected by the gravity, surface tension and inertia, it could be found that there were several reversals in the movement direction of liquid droplets. During the period of the droplet pulsation, due to the frictional resistance, the pulsation amplitude gradually decreased with respect to the dimensionless time. The kinetic energy of droplets increased with the tube spacing increasing when the liquid accumulated at the bottom of tubes, resulting in an increase in both the amplitude and number of pulsation. The amplitude and number of pulsation decreased with the increase of Re due to the droplet velocity decreasing.