Abstract: Objective To investigate the role and significance of platelet and leukocyte surface associated antibody (PAIg) in the pathogenesis of autoimmune thrombocytopenic diseases. Methods The platelet and leukocyte associated antibody levels in 205 cases of ITP patients, 64 patients with rheumatic disease accompanied by thrombocytopenia and 133 healthy people were detected and compared. Results The PAIgG levels in ITP patients and patients with rheumatic autoimmune diseases were increased compared with healthy controls. The PAIgA levels increase occurred only in ITP patients, while the patients of rheumatic autoimmune diseases and healthy controls was normal. The increase of PAIgM levels occurred only in patients with rheumatoid immune disease, but there was no significant difference between ITP patients and healthy controls. All three kinds of granulocyte associated antibodies were seen in patients with ITP and rheumatic disease. Conclusion Although ITP is defined as organ specific autoimmune diseases, the involvement of target cells not only focuses on platelet, at least also include white blood cell. PAIgG is not only present in ITP patients; the increase of PAIgA may more support the clinical diagnosis of ITP. The number of platelets reduction in patients with autoimmune thrombocytopenic diseases may be mainly mediated by PAIgM.