Calcium silicate carbonatable binder is an important direction to realize the green and sustainable development of building materials industry. In order to study the effect of calcium silicon ratio (n(CaO)∶n(SiO₂), molar ratio) on the composition of calcium silicate mineral phase and their carbon sequestration capabilities, calcium silicate carbonatable binders were synthesized with controlled calcium silicon ratio (n(CaO)∶n(SiO₂)=1.8~2.2). Techniques such as t-pH, XRD, TGA, and SEM were employed to examine the evolution of phase composition, carbonization hardening process, CO₂ uptakes and carbonization products of calcium silicate carbonatable binders. The results indicate that the content of γ-dicalcium silicate (Ca₂SiO₄, γ-C₂S) initially increases and subsequently decreases as the calcium silicon ratio rises. When the calcium silicon ratio is no higher than 2.0, the content of rankinite (Ca₃Si₂O₇, C₃S₂) gradually increases with the decreasing of calcium silicon ratio. When the calcium silicon ratio is higher than 2.0, the content of β-dicalcium silicate (Ca₂SiO₄, β-C₂S) progressively increases with the increasing of calcium silicon ratio. The reaction of carbonization for 0.5 h is intense, and the compressive strength initial increases and subsequent decreases as the calcium silicon ratio increases. The reaction produces calcite, aragonite and vaterite. With the content of C₃S₂ and γ-C₂S decreasing significantly, and the calcite content remains largely unchanged even when the carbonization reaction is extended to 24 h. C₃S₂ decelerates the early reaction of binder, but a more sustained carbonization reaction and a greater variety of carbonization products can enhance its subsequent compressive strength. The compressive strength and CO₂ uptakes after carbonization for 24 h reach 129.76 MPa and 18.57%, respectively.