To deal with the limitations of the existing constitutive relation models of confined concrete, the experimental results of confined concrete columns were collected to establish a database, including concrete strength of 19.6-158 MPa, volumetric ratio of 0.5%-7.27%, stirrup yield strength of 296-1 318 MPa, and longitudinal reinforcement ratio of 0%-5.87%. The effects of seven key parameters on the strength enhancement factor (K_c=f_cc/f_c) and deformation enhancement factor (Kε=ε_cc/ε_c) of confined concrete were analyzed. Through the unified processing and regression analysis of the data in the database, the unified equation of confined concrete stress-strain curve under axial compression was proposed, and the computation formulas of peak stress and peak strain were obtained. The prediction effects of the proposed unified equation and the existing models were compared and analyzed. Results show that the stress-strain curves obtained by the unified equation were more consistent with the experimental curves. The formulas of peak strain and peak stress had good predictive effect. From the overall verification results, it can be concluded that the model proposed in this paper is highly accurate and widely applicable.