CO₂ absorption property of Li₄SiO₄ was investigated by thermogravimetry under controlled P(CO₂) between 1.0 bar and 2x10^-2 bar. By using scanning type TG, equilibrium temperature of chemical reaction described as Li₄SiO₄+CO₂↔Li₂CO₃+Li₂SiO₃ at fixed P(CO₂) could be evaluated. The obtained equilibrium temperature and P(CO₂) by using particle with small diameter showed fair agreement with thermodynamically calculated ones. CO₂ absorption rate increased with increasing temperature or P(CO₂) and decreasing particle size. Under P(CO₂) larger than 0.3 bar, reaction kinetics could be explained with Jander model assuming Li⁺ diffusion as rate determining step. With decreasing P(CO₂) as small as 0.03 bar, it was suggested that reaction model varied to one with surface reaction as rate determining step.