Objective： To observe the effect of Zidianling on the metabolicpathway of tryptophan(Trp)mediated by indoleamine 2，3-dioxygenase(IDO)/tryptophanyl-tRNA synthetase(TTS)in patients with chronic immune thrombocytopenia(ITP)with yin-deficiency and blood-heat syndrome.Methods：Selected healthy volunteers(the normal control group)and patients with chronic ITP with yin-deficiency and blood-heat syndrome(the patient group)，20 cases in each group.The normal control group received no treatment，while the patient group received Zidianling for treatment.Before and after treatment，collected heparin anticoagulant specimens of patients，and detected the expression of IDO and TTS in CD4+and CD8+T of T lymphocytes as well as the concentration of Trp and Kyn in plasma.Results：There were 10 cases of complete reaction，in which 7 cases were effective and 3 cases were ineffective，with the total effective rate being 85.0%.Before treatment，the mean fluorescent intensity of IDO in CD4+and CD8+T of T lymphocytes in the patient group was lower than that in the normal control group(P ＜ 0.05)，and the mean fluorescent intensity of TTS was higher than that in the normal control group(P ＜ 0.05).After treatment，the mean fluorescent intensity of IDO in CD4+and CD8+T of T lymphocytes in the patient group was higher than that before treatment(P ＜ 0.05)，and the mean fluorescent intensity of TTS was lower than that before treatment(P ＜ 0.05).Before treatment，the concentration of Trp and Kyn in plasma in the patient group was higher than that in the normal control group，differences being significant(P ＜ 0.05).After treatment，the concentration of Trp in the patient group was lower than that before treatment，difference being significant(P ＜ 0.05)，and the concentration of Kyn in the patient group was higher than that before treatment，difference being significant(P ＜ 0.05).Conclusion：Zidianling may exert its clinical effect by influencing the metabolic pathway of Trp mediated by IDO/TTS in chronic ITP patients with yin-deficiency and blood-heat syndrome.