Using CO₂ gas carbonation treatment to recycled fine powder to replace cement to prepare cement mortars samples， the influence of recycled fine powder on the hydration and performance of mortar under different replacement ratios was investigated. The results show that when the replacement ratio is 20%， compared with the untreated recycled fine powder， the compressive strength of carbonated recycled fine powder mortar at 1 day and 3 days increases by 66.7% and 17.6%， respectively. The main components of the carbonated recycled fine powder are CaCO₃ and amorphous silica gel， which can react with the cement hydrates， thereby exerting the volcanic ash effect. The fine quartz sand in the recycled fine powder exhibits nucleation effect， accelerating the early hydration process of cement and significantly improving its early mechanical properties. During the accelerated carbonization process， the carbon sequestration of the recycled fine powder can reach 10.0% of its own mass. After preparing the mortar， its average unit compressive strength can reduce CO₂ emissions by up to 18%.