The characterization of CO2-modified recycled aggregates with different qualities and particle sizes is not systematic and comprehensive. Under 20% CO2 concentration and natural environmental pressure, considering the effect of recycled coarse aggregate (RCA) quality and particle size, the carbonization rate, CO2 absorption, alkalinity, water absorption of CO2-modified recycled coarse aggregate (CRCA) and residual CO2 in CRCA were investigated; the compressive strength and chloride penetration resistance of CO2-modified recycled coarse aggregate concrete (CRAC) were also evaluated; finally, its environmental benefits were assessed. The results show that the carbonization rate and CO2 absorption of CRCA increase with the increase of CRCA water-cement ratio; the CO2 modification significantly reduces the alkalinity of RCA; the smaller particle size and lower water-cement ratio of CRCA, the more CO2 sequestrates in CRCA; the CO2 modification remarkably reduces the water absorption of CRCA and significantly improves the compressive strengths and chloride penetration resistance of CRAC. The CO2 modification of recycled aggregate captures CO2, and reduces the construction material usage due to the enhanced properties of CRAC, which brings better environmental benefits.