Objective：To observe the curative effect of combination use of Expectorant Cough Mixture and western medicine on community acquired pneumonia (CAP) and its effects on the lung function and immune function of patients. Methods：A total of 96 CAP patients were selected and divided into the control group and the observation group according to the random number table method， with 48 cases in each group. The control group was given symptomatic treatment with western medicine， and the observation group was treated with Expectorant Cough Mixture based on the treatment of the control group. The changes in clinical effects， relief time of symptoms， inflammatory indexes [procalcitonin (PCT)， tumor necrosis factor- α (TNF- α) and hypersensitive C-reactive protein (hs-CRP)]， pulmonary function indexes [forced vital capacity (FVC)，forced expiratory volume in the first second (FEV1)，and FEV1/FVC] and immune function (levels of T lymphocyte subsets CD4+ and CD8+) were compared between the two groups. Results： The total effective rate was 95.83% in the observation group and 83.33% in the control group， the difference being significant (P＜0.05). The disappearance time of fever， cough， expectoration and lung rales in the observation group was respectively earlier than that in the control group， differences being significant (P＜0.05). After treatment， the levels of hs-CRP， PCT and TNF- α in the two groups were decreased when compared with those before treatment (P＜0.05)， and the above three indexes in the observation group were lower than those in the control group (P＜0.05). After treatment，the levels of FEV1， FVC and FEV1/FVC in the two groups were increased when compared with those before treatment (P＜ 0.05)，and the above three indexes in the observation group were higher than those in the control group (P＜ 0.05). After treatment，the levels of CD4+ and CD4+/CD8+ in the two groups were elevated when compared with those before treatment (P＜0.05)， and the levels of CD8+ in the two groups were reduced when compared with those before treatment (P＜0.05)； the levels of CD4+ and CD4+/CD8+ in the observation group were higher than those in the control group (P＜0.05)，and the levels of CD8+ was lower than that in the control group (P＜0.05). Conclusion：The combination use of Expectorant Cough Mixture and western medicine has a significant curative effect on CAP， which can mitigate the inflammatory responses， improve the lung function and immune function of the body.