To investigate the effects of Modified Dingchuan Decoction combined with anti-tuberculosis therapy for severe pulmonary tuberculosis and its influence on blood gas index.Methods:A total of 136 patients with severe pulmonary tuberculosis treated in Shanghai Pudong New District Pulmonary Hospital were selected as the study objects,and they were divided into observation group and control group with 68 cases in each group by random digital table method.The control group was given anti-tuberculosis therapy and observation group was treated with Modified Dingchuan Decoction based on the treatment of the control group.With one month taken as a course of treatment,and 2 groups were treated for 3 courses of treatment continuously.The clinical efficacy of 2 groups was counted.The changes of focus absorption,sputum negative rate and focal cavity closure of 2 groups after treatment were compared.The blood gas indexes and pulmonary function levels of 2 groups before and after treatment were compared and detected.Results:After treatment,the total effective rate of observation group and control group were 85.29% and 69.12% respectively,which showed that the total effective rate of observation group was significantly higher than control group (P<0.05).The sputum negative rate of observation group was significantly higher than that the rate of control group after treatment (P<0.01).After treatment,the proportion of patients with focal cavity closure in observation group was significantly higher than that in control group (P<0.01),and the proportion of patients with enlarged focal cavity closure was significantly lower than that in control group (P<0.01).Compared with before treatment,the level of PaCO2 in 2 groups decreased significantly,and observation group was significantly lower than control group (P<0.01).Compared with before treatment,the levels of PaO2,SpO2,OI and the levels of FEV1 and MMEF in 2 groups after treatment was significantly higher than that before treatment (P<0.01),and the levels in observation group were significantly higher than these in control group (P<0.05 or P<0.01).Conclusion:Modified Dingchuan Decoction combined with anti-tuberculosis treatment can effectively relieve the clinical symptoms of patients with severe pulmonary tuberculosis,improve the clearance rate of pathogenic bacteria,promote the focal cavity closure,and improve the blood gas indexes and pulmonary function of patients,whose clinical curative effect is outstanding.