Abstract: The mine rescue capsule is the equipment that provides interim measures and life support for underground survival in the mine accident. In the process of waiting for rescue, one of the key technologies of cabin air purification is to remove CO₂ in the capsule. And compared with other adsorbent, the sodium lime has the advantages of lower toxicity, more stable performance, easy to use and cheap, which are suitable properties as an adsorbent used for cabin air purification. In the 10 000 ×10^-6 and 8 000×10^-6 concentrations of CO₂, we test the adsorption performance of sodium lime in different fluid velocity（0.5 m/s, 1.0 m/s, 1.5 m/s）. The conclusion of this study shows that reducing the velocity of fluid can improve the sodium lime adsorption capacity of CO₂; the adsorption efficiency of soda lime decreased from 2% to 4% while the concentration of CO₂ increased from 8 000×10^-6 to 10 000×10^-6; and according to the calculation in the design conditions, mine rescue capsule needs to reserve at least 157.94 kg sodium lime in air conditioner & purifier AIO in the 106 hours .