In order to improve the mechanical properties of recycled concrete prepared from recycled aggregate from construction waste, recycled mortar and concrete were prepared by carbonized recycled fine aggregate instead of original recycled fine aggregate, and the effect of carbonized recycled fine aggregate on the mechanical properties of recycled mortar and concrete was studied. At the same time, X-ray diffraction (XRD) and mercury injection (MIP) were used to characterize the phase composition and pore structure of the recycled fine aggregate and recycled mortar after carbonization. The results show that the compressive strength and flexural strength of the recycled mortar prepared from recycled fine aggregate with carbonization treatment (7, 14, 28 d) are significantly increased, and the strength is positively correlated with the carbonization treatment time of recycled fine aggregate, and the strength increases the most in 28 d (compressive strength increases by 40.5% and flexural strength increases by 27.1%). The compressive strength of recycled concrete prepared from recycled fine aggregate with carbonization treatment (28 d) is improved (about 15.4%). XRD and MIP results show that Ca(OH)2 and other substances in the carbonized recycled fine aggregate are converted into CaCO3 after carbonization treatment, which reduces the porosity of the matrix by filling pores and microcracks, improves the shape and surface structure of aggregate particles, enhances its combination with the cement matrix, and optimizes the performance of recycled mortar and concrete.