Carbonation has been proven to be a promising way to improve the mechanism properties and durability of steel slag products. CA bacteria can promote the hydration of CO2. In this study, one kind of alkali-resistant CA bacteria was chosen to investigate its effects on the carbonation process of γ-C2S. Results showed that bacteria could increase the compressive strength of carbonized γ-C2S by 19.0%. Main products of carbonized γ-C2S were vaterite, calcite and SiO2 gel. The addition of bacteria could only accelerate the deposition of calcium carbonate, while hardly changing the types and properties of the carbonation products. Additionally, accelerated carbonation makes it harder for the carbon dioxide to diffuse inward, leading to the decline of accelerating carbonation effect. However, CA bacteria could change the morphology of calcium carbonated during the carbonation process of β-C2S and further accelerate the hydration process of β-C2S. The pore structure can also be refined with the incorporation of bacteria.