For better understanding of the mechanical property and constitutive relation of carbonated concrete under cyclic load, cyclic load and monotonic load tests were carried out on prism specimens. Considering the effect of section sizes on carbonated concrete member, the hysteresis loop and skeleton curve of the specimens were obtained, and the effects of carbonization on specimen failure mode, concrete strength, elasticity modulus, peak strain, and ultimate strain were analyzed from carbonation rate perspective. It's revealed that, because of the accumulated internal damage under cyclic load, the stress-strain curve of carbonated concrete decreased significantly, and the ductility was less than that under monotonic load. Furthermore, the peak strain of carbonated concrete decreased a little, peak stress increased, and ultimate strain decreased with the increase of carbonization depth. Based on the test results, under the consideration of carbonation rate and the introduction of the parameters at stress-strain curve descending branch, the stress-strain constitutive relation of carbonated concrete under cyclic load was established, which agreed well with the experimental values.