Objective To evaluate the clinical efficacy and safety of TanReqing Injection in the treatment of acute exacerbations of chronic obstructive pulmonary disease (COPD), and to observe its effects on the plasma levels of cytokine IL-17, IL- 8 and Leukotriene B4 in such cases. Methods A randomized, single blind controlled trial (RCT) was designed. Sixty hospitalized COPD patients with an acute exacerbation were randomly allocated to the treatment group (20 ml of TanReqing Injection iv gtt q 24 h) or the control group (20 ml of placebo Injection iv gtt q 24 h) based on the Guideline for Dignosis and Management of COPD issued by Chinese Society for Respiratory Disease and the Criteria of Dignosis and Efficacy Measures of Traditional Chinese Medicine Syndrome and Illness enacted by The State Administration of Traditional Chinese Medicine. All patients were received standard therapy. Each group contained 30 patients. The therapeutic course of both groups was 12 days. The criterias of TCM syndrome of retention of phlegm-heat in the lung were: cough with rough breath, accumulation of sticky or yellow thick sputum, cough with difficulty in expectoration, or accompanied by fever, thirst with desire of drink, red tougue with yellow fur, slippery and rapid pulse. Results According to the analysis on the basis of intention -to -treat and per-protocol population, it showed that the markedly effective rates were 70.00% and 72.41% respectively, and effective rates were 96.67% and 96.55% in the treatment group respectively. While in the control group the markedly effectiverates were 46.67% and 48.28% respectively, and effective rates were 86.67% and 89.65% respectively. Significantly lower plasma concentration of IL-17 and IL-8 in the treatment group was noted when compared with control group. There was a statistically significant difference between two groups (Plt;0.05). Conclusions TanReqing Injection shows a definite clinical effectiveness without obvious toxic-adverse effects in the treatment of patients with acute exacerbations of COPD and its mechnical function may related to the level of the excess expression of plasma cytokine IL-17, IL-8 in such cases.