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Objective: To explore the effects of paeoniflorin on Th17, Treg cell subsets and lung function in rats with chronic bronchitis （CB）, so as to enrich its pharmacological effects. Methods: CB model was established by compound induction in SD rats, and SD rats were randomly divided into CB group （normal saline）, low-dose paeoniflorin group （50 mg/kg）, medium-dose paeoniflorin group（ 100 mg/kg）, high-dose paeoniflorin group（ 200 mg/kg） and Helao group（ positive control, Helao oral liquid）, with 10 rats in each group; another 10 rats in the control group （normal saline） were given 2 ml/100 g corresponding drugs by gavage after modeling. After administration, the general conditions of rats were observed and the lung function and blood gas were analyzed; the morphology of lung tissue was observed by HE staining; the lung CD4+T, CD8+T, Th17（ CD4+IL-17+T） and Treg（ CD4+CD25+Foxp3+T） cells were detected by flow cytometry; the levels of IL-10, IL-22 and IL-17 in the lung were detected by ELISA. Results: In CB group, the activity of rats were slow, the color of hair were dim, the body were curled up, accompanied with cough and moist nasal cavity, the above symptoms and injuries were alleviated in different degrees in paeoniflorin groups and Helao group, and the high dose group was the least. Compared with control group, the airway resistance, arterial partial pressure of carbon dioxide （PaCO2）, IL-17, IL-22 levels, CD4+T, CD8+T, Th17 cells, Th17/Treg, CD4+T/CD8+T were higher in CB group, arterial partial pressure of oxygen （PaO2）, IL-10 and Treg cells were lower （all P<0.05）; compared with CB group, the airway resistance, PaCO2, IL-17, IL-22 levels, CD4+T, CD8+T, Th17 cells, Th17/Treg, CD4+T/CD8+T in low-, medium- and high-dose paeoniflorin groups decreased in turn, PaO2, IL-10 and Treg cells increased in turn （all P<0.05）; there was no significant difference in airway resistance and the other above indexes between the medium-dose paeoniflorin group and Helao group （P>0.05）. Conclusion: Paeoniflorin can regulate the activation of T lymphocytes, reduce the differentiation of Th17 cells, increase the differentiation of Treg cells, and reduce the inflammatory level and lung injury in CB rats. [ABSTRACT FROM AUTHOR]