To address the knowledge gaps of the cyclic stress-strain model of FRP-confined concrete, this paper presented the experimental results of CFRP-confined plain and RC square columns under monotonic and cyclic axial compression. The specimens were divided into two groups on the basis of size. The width of the cross section and the height of the total column were 305 mm, 915 mm and 204 mm, 612 mm for the two groups, respectively. Test results showed that the stress-strain curves of the CFRP-confined larger columns exhibited a localized strain-softening behavior, in which the confinement of CFRP wrap was moderately-confined and significantly influenced by size effect. Moreover, the ultimate compression strain, unloading curves and plastic strain were remarkably influenced by hoops. Based on the test data, a cyclic axial stress-strain model for FRP-confined square concrete columns was proposed. The proposed cyclic axial stress-strain model consists of three main components, namely (i) a monotonic stress-strain model to describe the envelope curve, (ii) a polynomial expression for the unloading curve, and (iii) a straight line for the reloading path. The influences of internal steel reinforcements, size effect and as well as the number of layers of CFRP wrap were considered. The good agreement between the predictions of the proposed model and the test results demonstrates the capability and accuracy of the proposed model.