To analyze the clinical efficacy of modified Qianjin Weijing Decoction in the treatment of severe pneumonia,and to explore the mechanism of the clinical efficacy,and to provide reference for the choice of therapy in severe pneumonia.Methods：A total of 106 cases of severe pneumonia admitted to Dazhou Integrated Traditional Chinese and Western Medicine Hospital in January 2016 to January 2018 were selected as research objects.According to the number of the patients,the odd-even grouping method was used.The odd was control group,and the even was observation group,with 53 cases in each group.The 2 groups were given routine treatment for severe pneumonia：empiric anti-infection treatment,target anti-infection treatment,oxygen therapy and auxiliary respiratory therapy and glucocorticoid therapy.On the basis of the treatment in the control group,the observation group was treated with modified Qianjin Weijing Decoction according to the patient's traditional Chinese medicine(TCM）syndrome.The 2 groups of patients were treated for 2 weeks.Clinical symptom-related indexes like scores of CURB-65 and APACHE Ⅱ,inflammatory response indexes like white blood cell(WBC),procalcitonin(PCT）and C-reactive protein(CRP),respiratory function indexes like oxygenation index,oxygen partial pressure(PaO2）and carbon dioxide partial pressure(PaCO2),and regulatory factors of immune balance like CD4+CD25+Treg cells,IFN-γ,IL-4 and IFN-γ/IL-4 of the patients in the 2 groups before and after the treatment were compared.The clinical efficacy of the 2 groups was determined and compared.Adverse drug reactions during the treatment were compared between the 2 groups.Results：1）After 2 weeks of the treatment,the total effective rate of the observation group was significantly higher than that of the control group(P<0.05). 2）After the treatment,the scores of CURB-65 and APACHE II in the 2 groups were significantly lower than those before the treatment,and the scores in the observation group were lower than those in the control group(P<0.05). 3）After the treatment,there was no obvious change in the IFN-γ of the 2 groups.The IL-4 and CD4+CD25+Treg cells were significantly lower than those before the treatment,and the IFN-γ/IL-4 was higher than that before the treatment(P<0.05).The IL-4 and CD4+CD25+Treg cells in the observation group were lower than those in the control group,and the IFN-γ/IL-4 was higher than that in the control group(P<0.05). 4）After the treatment,WBC,PCT and CRP of the 2 groups were significantly lower than those before the treatment,and those in the ovservation group were significantly lower than those in the control group(P<0.05). 5）After the treatment,the oxygenation index and PaO2 in the 2 groups were significantly higher than those before the treatment,and those in the observation group were higher than those in the control group(P<0.05); PaCO2 was significantly lower than that before the treatment,and that in the observation group was lower than that in the control group(P<0.05). 6）There was no significant difference in the rate of adverse drug reactions between the 2 groups(P>0.05).Conclusion：Qianjin Weijing Decoction can restore the immune balance of patients with severe pneumonia,reduce the inflammatory response and improve the respiratory function of the patients,so as to improve the clinical symptoms of severe pneumonia,improve the clinical efficacy,and do not increase the adverse drug reaction.It has high clinical value.