Objective: To investigate the protective effects of cinnamon polyphenols on streptozotocin-induced diabetic mice and its molecular mechanism. Methods: A single dose of streptozotocin (streptozotocin, STZ; 240 mg/kg) was used to induce diabetic mouse model. The rats were randomly divided into five groups: STZ model control group, metformin (0.3 g/kg), and low-, medium- and high-dose groups (0.3, 0.6 g/kg, and 1.2 g/kg) every day continuously until day 14. The vehicle control was set up. After the last administration, the fasting blood glucose (FBG) value was measured by blood glucose test. Serum amylase content was measured by biochemical method. The serum insulin and glucagon concentration were measured by enzyme-linked immunosorbent assay (ELISA). The number of insulin-positive cells in islet cells was analyzed and the expression of protein kinase B (AKT) and its phosphorylation level in pancreatic cells were detected by Western blotting. Results: Compared with diabetic mice, in the cinnamon polyphenols intervention groups the diabetic mice had significantly lower blood glucose (P<0.05), increased serum insulin, and decreased glucagon levels (P<0.05). The number of insulin-positive cells was significantly increased (P<0.05). The expression of protein kinase B (AKT) and its phosphorylation level in pancreatic cells increased in a dose-dependent manner. Conclusion: Cinnamon polyphenols show effective cytoprotective effects on streptozotocin-induced diabetic rats' pancreatic lesions, and their molecular mechanisms may be related to the promotion of islet β cell secretion by regulating pharmacological activities of the islet cell AKT signaling pathway.