In order to promote the application of recycled concrete powder (RCP) in alkali-activated slag (AAS) materials, this paper uses carbonization technology to improve the quality of RCP and replaces 10%~40% (mass fraction, the same below) granulated blast furnace slag (GBFS) with RCP to prepare AAS mortar. The effect of the dosage of carbonated recycled concrete powder (CRCP) on the hydration performance, mechanical strength, and microstructure of AAS mortar was investigated. The results show that main components of CRCP are fine-sized calcium carbonate and silica gel, which have high water absorption and can reduce the fluidity of AAS mortar. CRCP can promote hydration of GBFS by filling and activity effects, improving the packing density and pore structure of AAS mortar, thereby increasing compressive strength. It is observed that when CRCP content reaches 20%, the resulting AAS mortar exhibits an optimal compressive strength approximately 16%~20% higher than that achieved with non-carbonated RCP.