Objective:To study the protective effects of cinnamon on liver injury in diabetic rats. MethodsThe rats were randomly divided into the normal group and modeling group. Before modeling the rats were fasted for 12 hours but water was taken freely. Then the diabetes model was established in the modeling group by intraperitoneal injection of streptozotocin (STZ) at dose of 85 μg/g. Three days later,the rats with fasting blood glucose (FBG) value above 16.7 mmol/L were randomly divided into the model group and cinnamon group (1.5 g/kg). After administration for 25 days,the FBG of rats was measured,the body weight was recorded and the liver index was calculated. The serum activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and serum content of total protein (TP) and albumin (ALB) were detected. The serum activity of superoxide dismutase (T-SOD) and serum content of malondialdehyde (MDA) in rats were determined by hydroxylamine method and DTNB method,respectively. The levels of energy products in liver tissue including phosphocreatine (PCr),adenosine triphosphate (ATP),adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were detected by high performance liquid chromatography.  Results:Compared with the normal group,the blood glucose levels,liver index,serum levels of ALT, AST and MDA were significantly increased in the model group,and the body weight,serum contents of TP and ALB,serum activity of T-SOD and the levels of PCr and ATP in liver were significantly decreased(P<0.05,P<0.01). After treatment with cinnamon in model rats,the liver index,serum levels of ALT, AST and MDA were significantly decreased,and the serum contents of TP and ALB,serum activity of T-SOD and the levels of ATP,ADP and AMP in liver were significantly increased(P<0.05,P<0.01).  Conclusion:Cinnamon shows a certain protective effects on liver injury in diabetic rats,which is associated with the inhibition of oxidative stress and the regulation of hepatic energy metabolism.