Objective:To observe the clinical effect of Shengxueling (生血灵, SXL) on idiopathic thrombocytopenic purpura (ITP), and study the possible mechanism. Methods: Eighty-six cases of ITP were randomly divided into two groups. The SXL group, 56 patients treated with SXL, a traditinal Chinese medicine and 30 patients administered with prednisone were taken as control. Each group took drugs for 3 months and was under follow-up observation. Results: In the SXL group, the total effective rate was 85.71%, similar to prednisone 83.33% (P＞0.05) for 3 months, but the total effective rate of SXL (91. 07%) were obviously better than that of the control group (53.33 %) (P＜0.01) for 6 months and had no obvious adverse reaction.The patients bleeding was alleviated or stopped, the general condition was improved. At the same time,blood platelet count (PLT) was increased, platelet associated immunoglobulin (PAIg) and interleukin-4 (IL4) were markedly dropped, the level of natural killers cells activity (NKa) increased, the rate of T lymphocyte subsets gradually returned to normal level. Megakaryocyte tended to maturation on bone marrow smear after treatment. All differences above were statistically significant. Conclusion: SXL is an effective and safe medicine for ITP. Its mechanism could regulate cytoimmune, inhibit platelet antibody to reduce the destruction of platelet, increase the number of platelet, promote the division and maturation of megakaryocyte, facilitate the production and release of platelet, lower the fragility of capillary, prevent and cure hemorrhagic tendency.