In order to study effect of cement paste mix sequestration carbon dioxide on cement properties, different states and dosages of carbon dioxide were added to fresh cement paste. The carbon sequestration effect and mechanical properties of fresh cement paste were tested, and characterization methods such as TG-DTG, MIP, SEM were used to explore the effect of carbon dioxide on strength and microstructure of cement. The results show that when the water-cement ratio is 0.50, gas state carbon dioxide dosage is 1.5% (mass fraction), the compressive strength and carbon sequestration effect of cement are optimal. The compressive strength increases by 100% at 3 and 7 d, and by 139.6% at 28 d. After adding carbon dioxide, pores with diameters between 100~600 nm almost disappear while pores below 100 nm significantly increase, effectively reducing harmful pores inside cement matrix and enhancing pore structure in hardened cement paste. Carbon dioxide is directly accelerating cement early hydration. The growth state and bonding mode of hydration products are optimized to achieve carbon sequestration and strengthening of cement-based materials.