Based on the Duncan-Chang model and the equivalent additional stress effect of geocell reinforcement，an equivalent strength and stiffness model tailored for shear-contractive soils reinforced with geocells has been formulated. This model was further developed using the UMAT subroutine module of the ABAQUS software. To validate the effectiveness of the model and the correctness of the UMAT subroutine，triaxial tests and foundation bearing capacity model tests were conducted. The results reveal that at low axial strains，the strength ratio   between reinforced and unreinforced soils is less influenced by natural density. However，as the axial strain increases，clays with higher natural densities will exhibit a greater   value. The developed UMAT subroutine shows good agreement with experimental data up to an axial strain of 0.15，with minor deviations thereafter but overall low relative errors，confirming the validity of the reinforced clay model and the correctness of the secondary development of the UMAT subroutine. Prior to reaching peak strength，both the proposed model and the discrete reinforcement-soil model align well with experimental results. After reaching peak strength.，the numerical simulation results of the proposed model are closer to experimental outcomes. Additionally，this model offers advantages of simplified modeling and high computational efficiency. For settlement values S≤4 mm，the load-displacement curves of both unreinforced and reinforced sandy soil models align well with experimental data. When S＞4 mm，the calculated bearing capacity of the models is slightly higher than experimental data. The research outcomes of this study can provide a model reference for geocell-reinforced shear-contractive soils and offer new methods for finite element analysis in their engineering applications.