Abstract: Objective To explore the role of berberine in gestational diabetes mellitus (GDM) rat induced by high fat diet and low-dose STZ and its possible mechanisms. Methods After female SD rats were fed with high-fat diet for 5 weeks, STZ (25 mg/kg) was intraperitoneally injected on the first day after conception to establish the GDM rat model. The treatment of berberine by intragastric injection was from 1th to 19th day of pregnancy. The changes of fasting blood glucose and insulin resistance index in each group during pregnancy were detected. Pregnancy was terminated by caesarean on the 20th day of pregnancy, fetal and placental weights were measured and liver tissues were collected. The levels of TNF-α and CRP mRNA and protein were detected by real-time fluorescence quantitative PCR and ELISA; the expression of IKKβ and NF-κB protein was detected by Western blotting. Results Compared with normal pregnancy group, the fasting blood glucose and insulin resistance index of model group was significantly higher (all P<0.05), meanwhile fetal and placental weight increased (all P<0.05), the expression of CRP and TNF-α mRNA and protein in liver tissues was significantly increased, and the expression of IKKβ protein and nuclear protein NF-κB increased (all P<0.05). After treatment of Berberine, the expression of IKKβ, nuclear NF-κB, CRP and TNF-α in liver tissues of the model group was significantly decreased, the fasting blood glucose and insulin resistance index also decreased (all P<0.05). Conclusion Berberine can reduce inflammation in liver tissues, improve insulin resistance, and lower blood glucose levels in GDM rats through the inhibition of NF-κB nuclear transfer via IKK/NF-κB signaling pathway.