Red clay is widely used in foundation, roadbed, dam seepage prevention and other projects as a natural building material. However, it takes a long time for saturated red clay to consolidate and drain, so its shear characteristics in the process of self-stabilization are not clear. Consolidated-drained (CD) triaxial tests were conducted on saturated red clay under varying dry densities and confining pressures to investigate its stress evolution, deformation mechanisms, and strength variation patterns, ultimately developing a constitutive model for consolidation and drainage behavior. The results show that the stress-strain curve of saturated red clay takes strain ε₁=10% as the critical value dividing two stages elastic deformation and strain hardening, its strain shows hardening characteristics and the bulk strain undergoes linear growth and dilatancy failure process. The obvious dilatation phenomenon appears, and the effective stress undergoes rapid growth and stress strengthening stage. The stress paths of saturated red clay are all parallel straight lines with linear growth, the cohesion gradually increases with the increasing dry density, the internal friction angle increases slowly with the increasing dry density, and the shear strength gradually increases with the increase of confining pressure. Based on the results of triaxial tests on saturated red clay, a constitutive model for the consolidation drainage index of saturated red clay is proposed. The calculated failure ratio (R_f) of red clay ranges from 0.86 to 0.99, showing a decreasing trend with increasing confining pressure. The stress-strain characteristics exhibit strain hardening behavior. The developed model effectively captures the deformation behavior of saturated red clay under consolidated-drained conditions, providing a theoretical framework for investigating strain evolution in shear zones of lateritic landslides and offering critical insights to facilitate advanced research on slope monitoring and early-warning systems.