It was long believed that platelets are prematurely destroyed in the reticuloendothelial system by platelet autoantibodies in idiopathic thrombocytopenic purpura. However, humoral mechanisms cannot account for all observations made in this disorder, and it is increasingly evident that cellular mechanisms contribute to platelet destruction. In this review the tolerance of T cell, abnormality of T cell apoptosis, abnormal activation of T cells, T cell subtype and its function changes, and T cell-mediated cytotoxicity were summarized.