OBJECTIVE: To explore the mechanism of the Qinghe detoxification and Fuzheng formula, Toxin Clear, in the treatment of pneumonia by regulating the neutrophil extracellular trapping network through the MEK/ERK pathway. METHODS: Tracheal drip injection of Klebsiella pneumoniae was used to establish a mouse model of pneumonia. The mice were divided into blank group, model group, ceftriaxone group, toxin clear low dose group, and toxin clear high dose group. The pharmacodynamic effects of toxocarb on mice with pneumonia were evaluated in terms of general condition, alveolar lavage fluid cell count, and lung pathology; the kit detected the MPO viability in lung tissues; ELISA detected the changes of TNF-α and IL-6 content in lung tissues; and qRT-PCR detected the TNF-α, IL-6, IL-1β, Ly6G, MPO, NE, and Cit-H3 in lung tissues, PAD4 mRNA expressio;IHC to observe the expression of Ly6G, MPO, NE, and Cit-H3 in lung tissue sections;IF observation of NETs expression in lung tissue sections;Western blot method to detect the expression of MEK, P-MEK, ERK, P-ERK, PAD4, Cit-H3 proteins in lung tissues; RESULTS: Compared with the blank group, the cell counts of alveolar lavage fluid of mice in the model group were significantly elevated (P < 0.01), with a large number of inflammatory cell infiltration, alveolar edema and alveolar wall thickening in the lung tissues; the vitality of MPO in the lung tissues was significantly elevated (P < 0.01); the expression of TNF-α and IL-6 in the lung tissues was elevated (P < 0.01); the expression of TNF-α, IL-6, IL-1β, Ly6G , MPO, NE, Cit-H3, and PAD4 mRNA expression was elevated (P < 0.01); Ly6G, MPO, NE, and Cit-H3 expression was elevated in lung tissue slices (P < 0.01);NETs expression was elevated in lung tissue sections (P < 0.01); and p-MEK/MEK and p-ERK/ERK ratios, PAD4, and Cit-H3 protein expression were significantly elevated in lung tissue (P< 0.05 or P< 0.01)Toxocin intervention for 3 days could effectively improve the symptoms of shortness of breath, reduced activity and weight loss in mice with pneumonia, and reduce the infiltration of inflammatory cells in lung tissues and lung tissue damage; the high dose of toxocin reduced the number of cells in alveolar lavage fluid (P < 0.05); toxocin in all groups reduced the viability of MPO in lung tissues (P<0.05 or P<0.01); and reduced the expression of TNF-α, IL -6 expression in lung tissue (P<0.05 or P<0.01), and reduced inflammatory response; the low-dose group of toxocarbamol reduced the expression of TNF-α and IL-1β mRNA in lung tissue (P<0.01); the high-dose group of toxocarbamol reduced the expression of IL-6 mRNA (P<0.01); and the various groups of toxocarbamol significantly reduced the expression of Ly6G, MPO, NE, Cit-H3, and PAD4 mRNA expression (P< 0.01); decreased Ly6G, MPO, NE, and Cit-H3 expression in lung tissue sections (P< 0.05 or P< 0.01); decreased expression of NETs in lung tissue sections(P< 0.01); toxocarbophilus high dose group decreased lung tissue p-MEK/MEK protein expression (P< 0.01); toxocarbophilus groups decreased lung tissue p-ERK/ERK ratio, PAD4, Cit-H3 protein expression (P< 0.05 or P<0.01). CONCLUSION: MEK/ERK promote the formation of NETs involved in the development of pneumonia. Toxin clear inhibits the formation of NETs through the regulation of MEK/ERK and then attenuates the inflammatory response in the lung.