Acute ITP platelets are markedly reduced, usually less than 20 x 109/L. Platelet lifespan is markedly shortened, approximately 1-6 hours. Bone marrow examination most of the history megakaryocytes increased or normal, where the infantile megakaryocytes significantly increased. Chronic ITP mostly this test thrombocytopenia, mostly (30-80) × 109/L. Bone marrow megakaryocytes mostly increased, basically normal size, increased granular type, and significantly reduced platelet formation. Platelet surface-associated IgG was increased and platelet-associated C3 was increased. Platelet lifespan is shortened, about 1 to 3 days. The diagnostic criteria are as follows: 1. Decreased platelet count on multiple laboratory tests. 2. The spleen is not enlarged or only mildly enlarged. 3, Increased or normal megakaryocyte count on bone marrow examination with maturation disorders. 4.Any of the following five points should be present (1) Prednisone treatment is effective. (2) Treatment with splenectomy is effective (3) PalgG is increased. (4) PAC is increased. Shortened platelet life span. (5) Exclude secondary thrombocytopenia.