Objective To investigate the clinical effect of Tanreqing Injection on patients with severe pneumonia. Methods A total of 42 patients with severe pneumonia were randomly divided into control group and treatment group, with 21 patients in each group. The patients in the control group were given conventional Western medicine treatment, and those in the treatment group were given Tanreqing Injection in addition to the treatment in the control group; each course of treatment was 7 days. Arterial partial pressure of carbon dioxide (PaCO2) and oxygenation index (OI) were used to evaluate the improvement in respiratory function after treatment; white blood cell count (WBC), high-sensitivity C-reactive protein (hs-CRP), and procalcitonin (PCT) were used to evaluate the changes in inflammatory indices after treatment; Acute Physiology and Chronic Health Evaluation Ⅱ (APACHEⅡ) score and Clinical Pulmonary Infection Score (CPIS) were used to evaluate disease severity before and after treatment; clearance rate of pathogenic bacteria and clinical outcome were compared between the two groups. Results After treatment, both groups had a significant reduction in PaCO2 (P<0.05) and a significant increase in OI (P<0.05), and compared with the control group, the treatment group had a significantly greater reduction in PaCO2 and a significantly greater increase in OI (P<0.05). After treatment, both groups had significant reductions in WBC, hs-CRP, PCT, APACHEⅡ score, and CPIS (P<0.05), and the treatment group had significantly greater reductions than the control group (P<0.05). The treatment group had a significantly higher clearance rate of pathogenic bacteria than the control group (71.43% vs 38.10%, P<0.05）. There was a significant difference in the distribution of clinical outcomes between the two groups (P<0.05). Conclusion For patients with severe pneumonia, Tanreqing Injection can improve respiratory function, alleviate inflammatory response, enhance the bactericidal effect in combination with antibiotics, and significantly improve clinical outcome.