In order to study the influence of stirrup corrosion level on the failure modes, peak stress, peak strain, ultimate strain and shape of stress-strain curve of the confined concrete，15 reinforced concrete prism specimens are subjected to acid rain erosion in the acid environment modeled by artificial climate simulation technique followed by axial compression tests. Based on the Mander’s model and the existing research results, the calculation formulas for the peak stress，peak strain, ultimate strain and shape factor of the uncorroded specimens are determined. The factor calculation formulas for peak stress, peak strain, ultimate strain and shape factor of corroded specimens are developed by regression analysis of test data, respectively, and then the constitutive model of confined concrete by acid rain erosion is established. By comparing the simulation results with the experimental data, it can be found that all the peak stress, peak strain, ultimate strain and stress-strain curves shape of the specimens obtained by proposed method are in good agreement with the experimental data. Thus, the constitutive mode for confined concrete established in this paper can accurately reflect the mechanical performance of RC prism specimen by acid rain erosion, indicating its adaptiveness for estimating the residual bearing capacity and the seismic performance of RC structure under the acid rain environment.