The storage of CO₂ into saline aquifers is the best way to mitigate the green house effect. The storage of CO₂ in deep saline aquifers mainly concerns the water storage, the residual gas storage, the dissolved storage and the mineral storage. The hydrodynamic trap is formed by the upward movement of CO₂ to dense layers, which is trapped and aggregated in the geological body. The hydrodynamic traps include the open and the enclosed traps. The advantage of an enclosed trap is that the migration of CO₂ is confined both horizontally and vertically, and the disadvantage is that the dissolution is restricted by the limited gas-water contact area. The advantage of an open trap is the significant quantity of CO₂ dissolution caused by a large area of gas-water contact, and the disadvantage is the need of fine characterization of a large area to determine the possible gas leakage path and the need of regional monitoring. Due to the lag of the displacement and sucking phase permeability, a part of CO₂ is stored as the residual gas to form the residual gas trap. The CO₂ dissolved in water reacts with the ions of calcium, magnesium and iron, to generate carbonate minerals, and to form the dissolved storage. The mineral storage formed by the slow chemical reactions between CO₂ and reservoirs rocks would generate carbonate minerals or bicarbonate ions. With different storage durations, the various storage methods play different roles, and the storage security levels also vary. The study of the storage mechanism of CO₂ in saline aquifers will provide some guidance for China's CO₂ sequestration project.