Steel slag is the waste residue of crude steel smelting, and its application in building materials is limited by its poor volume stability and poor cementitious reactivity. In this paper, the properties of aggregate and concrete are improved by carbonizing steel slag aggregate and steel slag permeable concrete. The results show that calcium carbonate will be formed in the pores of steel slag aggregate during carbonization curing, which will improve the compactness of the aggregate. The crushing index and water absorption of the aggregate will decrease by 24.7% and 49.7% respectively after 2 h carbonization curing. Replacing 40% cement and 40% natural aggregate with steel slag powder and carbonized steel slag aggregate will reduce the compressive strength of permeable concrete, but the 28-day compressive strength of permeable concrete can be increased by 45.5% through 2 h carbonization curing, and the carbon fixation of cementitious materials can reach 12.4%. Due to the decrease of porosity, the permeability coefficient of carbonized steel slag permeable concrete is 2.4 mm/s, which is 13.1% lower than that of non-carbonized steel slag permeable concrete.