CO2 solidified carbonate material is defined as a calcium carbonate-based composite material with a rapid strength obtained via the carbonation reaction of carbonatable binders with CO2 under normal conditions. In this paper, the mechanical properties and product composition of the CO2 solidified carbonate materials with Fe doping, chitosan inducing and curing regime designing were investigated as γ-C2S was used as a carbonatable binder. The results show that the enhancing strategies have a conflicting connection with one another. The Fe-γ-C2S group with chitosan inducing (i.e., 200 MPa after 24 h curing) and the chitosan induced γ-C2S group with long curing time (i.e., 230 MPa after 7 d curing) have a high strength. The crystalline form of calcium carbonate in γ-C2S group is mainly aragonite, while the calcium carbonate in Fe-γ-C2S group is calcite. The product composition of the CO2 solidified carbonate material is another crucial factor influencing the strength. The CO2 solidified carbonate material with an ultra-high strength has a structural feature, i.e., chitosan connects two phases (silica gel and calcium carbonate), and calcite exists inside in the calcium carbonate layer and aragonite outside. The presence of calcite can provide the strength at early curing stage, while aragonite occupies the main pore space on the outside, providing a diffusion channel for CO2 at the later curing stage.