Encapsulation and decapsulation characteristics of cation-exchanged LTA zeolite as oxygen gas storage media were investigated by means of intracrystalline high pressure encapsulation technique. The storage efficiency of Na-LTA containing K⁺ and Cs⁺ ions was measured in terms of Vo₂, the maximum capacity for encapsulated oxygen gases under a defined set of conditions. Na-LTA containing 27% K⁺ ion seems to be the best one for the encapsulation of oxygen gas molecules with the most eficient control of 8-ring window opening. But this system reveals the slow releasing of encapsulated molecules at ambient temperature. Na_8.5K_1.6Cs_1.9-LTA system containing 53% Cs⁺/++K⁺ was confirmed as the best efficient stroage media of oxygen molecules.