To explore the therapeutic effect and related mechanism of Qinghao Mahuang Decoction on patients with community-acquired pneumonia(CAP).Methods:A total of 230 patients with CAP treated at Xichang People's Hospital from January 2020 to August 2022 were enrolled and randomly divided into a control group and an observation group using a random number table method,with 115 patients in each group.The control group received conventional Western medicine treatment,while the observation group received Qinghao Mahuang Decoction in addition to the conventional treatment.The two groups were compared in terms of Acute Physiology and Chronic Health Evaluation Ⅱ(APACHE Ⅱ) score,length of hospital stay,C-reactive protein(CRP),white blood cell count(WBC),and procalcitonin(PCT) levels.Additionally,levels of Th1/Th2 cytokines and T lymphocyte subgroups were measured,and the therapeutic efficacy of the two groups was compared.Results:After treatment,the observation group had significantly lower APACHE Ⅱ scores,CRP,WBC,and PCT levels than the control group(P<0.05).Compared with the control group,the observation group had higher levels of CD4+T cells and interferon-gamma(IFN-γ),and lower levels of CD8+T cells,interleukin-2(IL-2),and interleukin-4(IL-4)(P<0.05).The observation group also had a shorter length of hospital stay than the control group(P<0.05).The treatment efficacy of the observation group was significantly higher than that of the control group(P<0.05).Conclusion:Treatment with Qinghao Mahuang Decoction in patients with CAP can reduce the severity of inflammation,improve immune function,and promote recovery,showing significant therapeutic effects.