[abstracts] Objective To investigate the effects of ursolic acid (UA) on TLR4/NF-κB signaling pathway and Th17/Treg cells in type 1 diabetes (T1DM) rats. Mmthods The T1DM rat model was prepared by intraperitoneal injection of streptozotocin, and randomly divided into blank (Control group) group, model group (Model group), metformin group (MET group) and UA group. General conditions such as body weight and blood glucose were recorded, and peripheral blood and pancreatic tissues were collected after six weeks of gavage to assess insulin intervention. Immunohistochemistry was used to observe the pathological changes in pancreatic tissues; horseshoe crab reagent was used to detect the changes in serum LPS content; qRT-PCR was used to detect the expression of pancreatic TLR4, MyD88, IκBα, and NF-κB p65 mRNAs, as well as the expression of the transcription factors RORγt and Foxp3 mRNAs; and Western blot was used to detect the expression of pancreatic TLR4, MyD88, IκBα , NF-κB p65 protein expression, and transcription factors RORγt, Foxp3 protein expression; flow cytometry to detect changes in the ratio of peripheral blood Th17, Treg cells; ELISA to detect changes in serum TNF-α, IL-6, IL-1β levels. Results After STZ-induced diabetic rats were treated by gavage for 6 weeks, compared with the Model group, fasting blood glucose (FBG) decreased significantly in both the MET and UA groups, and body weights increased; inflammatory infiltration of pancreatic β-cells was reduced; and the expression of TLR4, MyD88, IκBα, NF-κB p65, RORγt mRNA and protein expression was significantly decreased; LPS content was significantly decreased; IκBα, Foxp3 mRNA and protein expression was significantly increased; Th17/Treg ratio was significantly decreased; and TNF-α, IL-6, and IL-1β content was significantly decreased. Conclusion UA can improve the symptoms of rats by reducing LPS shift, inhibiting TLR4/NF-κB pathway, down-regulating RORγt and up-regulating Foxp3 expression to correct the imbalance of Th17/Treg cell ratio in T1DM rats.