Objective To investigate the effects of trigonelline (TRG) on lipid metabolism and insulin resistance in gestational diabetes mellitus (GDM) rats. Methods Eight female Wistar rats were randomly selected for normal feeding, and the remaining rats were fed a high fat diet for 8 weeks. After cage mating to confirm pregnancy, normal fed rats were used as the control group, and the high fat fed rats were intraperitoneally injected with 35 mg/ kg streptozotocin to induce the GDM model. Model rats were randomly divided into model, TRG low-dose (15 mg/ (kg·d)), TRG high-dose(45 mg/ (kg·d)) and metformin hydrochloride (MH) (200 mg/ (kg·d)) groups with eight rats in each group. Control and model groups were treated with the same amount of normal saline by intragastric administration for 14 consecutive days. Weigh and the fasting blood glucose (FBG) were measured. BM and the contents of 24 h Alb, AST, ALT, BUN, and SCr, serum high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), total cholesterol(TC), and triglyceride (TG) were measured. Fasting insulin (FINS) content was measured in each group. Insulin resistance index (HOMA-IR) and insulin sensitivity index (HOMA-ISI) were calculated. Histopathological changes of the pancreas in rats were observed. Levels of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6) in pancreatic tissues were measured. Results The GDM rat model was successfully established. Compared with the findings in the control group, FBG, serum LDL-C, TC and TG, FINS, HOMA-IRI, MDA, and TNF-α and IL-6 levels in pancreatic tissue were increased, serum HDL-C content, HOMAISI, and SOD and CAT activities in pancreatic tissue were decreased in model, TRG low-dose, TRG high-dose, and MH groups (P<0. 05), and pathological changes of various degrees were found in pancreatic tissue. Compared with the findings in the model group, in TRG low-dose, TRG high-dose, and MH groups, FBG, serum LDL-C, TC and TG, FINS, HOMAIRI, MDA, and TNF-α and IL-6 levels in pancreatic tissue were decreased, serum HDL-C content, HOMA-ISI, and SOD and CAT activities in pancreatic tissue were increased ( P< 0. 05), and pathological injury of pancreatic tissue was gradually decreased. The effect of TRG in low-dose, high-dose, and MH groups was gradually enhanced (P<0. 05). Conclusions Trigonelline reduces the blood glucose level, improves liver and kidney functions, and abnormal blood lipid metabolism, reduces insulin resistance and improves insulin sensitivity in GDM rats. Its effect may be related to reducing inflammation and oxidization.