Based on the linear and reverse linear differentiation models of CD8⁺ memory T cells, mathematical models were set up respectively and the dynamics of different T subpopulations was studied. It was found that when invading antigen with optimal dose of, both models can generate memory and fit well with experimental data. Further study found that CD8⁺ T cell memory relates strongly to the persistence of antigen. Thus the contribution of antigen to maintenance of T cell memory is reconfirmed. The effect of the life-span of memory cells on immune memory was also investigated. Reverse linear differentiation model is deemed to have advantage in generation of immune response and memory.