In view of the problems that CO2 is easy to corrode Portland cement stone, damage the structural integrity of cement stone and induce interlayer sealing failure, this paper uses slag to modify calcium aluminate cement, and studies the change law of compressive strength of calcium aluminate cement-slag system at 60, 80, 100, 120 ℃ and pure CO2 conditions. The effect of CO2 corrosion on hydration products and microstructure of calcium aluminate cement-slag system were investigated by X-ray diffractometer, thermogravimetric analyzer and scanning electron microscopy. The results show that compared with pure calcium aluminate cement stone, the slag transforms the hydration product of calcium aluminate cement stone into C2ASH8, which greatly improves the early compressive strength of cement stone. When the mass ratio of calcium aluminate cement to slag is 5∶5, the compressive strength of calcium aluminate cement increases by 215.4% after curing at 60 ℃ for 14 d. After CO2 corrosion, the hydration products of calcium aluminate cement-slag system change from C2ASH8 to C2AS, and CaCO3 is formed, which increases the density of corrosion layer. The compressive strength of cement stone increases with the increase of corrosion time at same temperature.