The potential of Li3NaSiO4 as CO2 absorption/desorption material was investigated. Preparation mechanism of Li3NaSiO4 by solid state reaction method was analyzed by thermal analyses. Li3NaSiO4 powder with high purity was successfully obtained by solid state reaction of Li4SiO4, Li2SiO3 and Na2CO3 without generation of liquid phase of LiNaCO3 during heat-treatment. It was proposed that Li3NaSiO4 layer with thickness of ~1 μm formed at interface between liquid LiNaCO3 and solid Li2SiO3 prevented CO2 desorption reaction; however, stable cyclic property of CO2 absorption/desorption with 20 times by alternate changing of CO2 and N2 gas at high temperature was successfully observed in Li3NaSiO4 because form of Li2SiO3 generated at CO2 absorption reaction by Li3NaSiO4 was needle-like with short edge of ~2 μm, which was small enough to complete CO2 desorption reaction. The cyclic property by alternate changing of 10% CO2/N2 and N2 was also obtained at 650 ºC, which was optimized using the pseudo van’t-Hoff plot prepa