Abstract：Objective：To observe the clinical effect of modified Dachaihu tang in adjuvant treatment of severe pneumonia. Methods：A total of 70 cases of patients with severe pneumonia were randomly divided into the control group and the study group， 35 cases in each group. The control group was given routine treatment with Piperacillin Sodium and Tazobactam Sodium for Injection and Meropenem for Injection，and the study group was additionally treated with modified Dachaihu tang based on the treatment of the control group. Both groups were treated for seven days. The changes in the levels of white blood cells(WBC)，C-reactive protein(CRP)，and procalcitonin(PCT) before and after treatment，the antipyretic time，and the disappearance time of coughing， panting and pulmonary moist rales were observed. Results： After treatment， the antipyretic time and the disappearance time of coughing，panting and pulmonary moist rales in the study group were shorter than those in the control group，the difference being significant(P＜0.05). After treatment，the levels of WBC，CRP and PCT in the two groups were decreased when compared with those before treatment(P＜0.05)，and the above levels in the study group were lower than those in the control group(P＜0.05). Conclusion： The therapy of modified Dachaihu tang combined with routine western medicine for severe pneumonia has significant curative effect and can effectively improve inflammatory responses in patients and quickly relieve the clinical symptoms，whose curative effect is better than that of simple western medicine.