To explore the role of CD72 in B lymphocytes of immune thrombocytopenic purpura (ITP) patients, the expression detection and in vitro culture experiment of patients’ and controls’ lymphocytes were made.The CD72 expressions on B lymphocytes were detected by flow-cytometry. The B cell proliferation were determined by method of 5-bromo-2’-deoxyuridine incorporation in culture of lymphocytes. The secretion levels of antibodies against human platelet antigens(HPA) and the cytokines related with B cell proliferation were measured by ELISA method. We found the CD72 expressions significantly increased in B cells of newly diagnosed or persistent ITP comparing with ITP in remission (P=0.018). B cell proliferation in culture with CD72 antibody addition significantly decreased in ITP patients and control group by comparing with isotype antibody addition (P=0.007 and 0.026 respectively). But there wasn’t significant differences of HPA antibody levels between CD72 antibody and isotype antibody added ITP patients’ cell cultures(P=0.91). IL-1 and macrophage migration inhibitory factor (MIF) levels of CD72 antibody added ITP patients’ cell culture supernatant were significantly higher than those of isotype antibody added culture supernatant (P=0.011 and 0.002 respectively). But that differences were not significant in cell cultures of control group, and we didn’t find significant differences of midkine or hepatocyte growth factor levels between CD72 and isotype antibody added culture supernatant. So we concluded that CD72 expression elevation related with active status of ITP, and the blockade of CD72 with antibody had negative impact on B cell proliferation and accompanied IL-1 and MIF increment in the culture of ITP lymphocytes.