Abstract: OBJECTIVE To explore the effects of external application of Rhei Radix et Rhizoma extracted by different processes on JAK2/STAT3 signaling pathway in mice infected with Mycoplasma a(MP), and to investigate the target of improving pulmonary inflammation in mice. METHODS Forty BALB/c mice were randomly divided into normal group, model group, raw powder group and ethanol extract group, with 10 mice in each group. Except the normal mice, the other 3 groups were infected with MP by nasal dropping. After the model was established, the corresponding drugs of each group were applied to the Back-Shu acupoint area of mice for 30 min·d^-1 for 7 consecutive days. On the 7th day after administration, pathological sections of lung and skin of mice were observed under light microscopy. Lung histopathological scores and lung index were calculated. IL-6 content in serum and lung tissue was detected by ELISA. STAT3, JAK2 protein and mRNA expression were detected by Western blotting and qPCR. RESULTS After MP infection, the alveolar septum, bronchiolar wall, inflammatory cell infiltration, lung index, inflammatory pathological score of lung tissue, IL-6 content in serum and lung tissue, the protein expression and mRNA content of STAT3 and JAK2 in lung tissue of mice were all increased(P<0.05). After treatment, lung index, pathological score of pulmonary inflammation, IL-6 content in serum and lung tissue of mice were decreased (P<0.05), and the effect of ethanol extraction group was more obvious than that of raw powder group, but there was no significant difference in serum content. Compared with model group, the contents of STAT3, JAK2 protein and mRNA in ethanol extract group and raw powder group decreased(P<0.05). CONCLUSION External application of Rhei Radix et Rhizoma ethanol extract can effectively improve the pulmonary inflammation in mice infected with MP and down-regulate the expression of IL-6, JAK2 and STAT3, which provides reference for its treatment of MP pneumonia.