Abstract: Objective To study the effects of rutin on myocardial enzyme in serum and myocardial morphology in diabetic mice induced by streptozotocin (STZ). Methods A model of type 1 diabetic mice was established in 48 male kunming mice with daily intraperitoneal injection of streptozotocin (STZ) 62.5 mg/kg for 5 consecutive days. 12 male Kunming mice were selected as normal group randomly. The established successfully diabetic mice were randomly divided into the model group, irbesartan group45 mg/(kg·d), low-, high-dose rutin groups50, 100 mg/(kg·d). The mice in the normal and the model groups were given sodium carboxymethyl cellulose solution (CMC-Na, 1 g/L) by intragastric administration respectively. After administration for 8 weeks, the levels of creatine kinase (CK), creatine kinase isoenzymes (CK-MB), hydroxybutyrate dehydrogenase (HBDH), and lactate dehydrogenase (LDH) in serum were detected by blood biochemical analyzer. The cardiac myocardial morphology was observed by HE staining, Masson trichrome staining and electron microscope. Results Compare to the normal group, the levels of the myocardial enzyme in serum evidently increased in the model group (P<0.01); Compare to the model group, the levels of the myocardial enzyme in serum decreased in low-, high-dose rutin groups; The levels of HBDH and LDH declined remarkably in the high-dose rutin group relative to the low-dose group (P<0.05); Compared to the high-dose group, the level of LDH increased in the irbesartan group (P<0.05).Moreover, relative to the model group, the morphology of myocardial tissue, the degree of fibrosis and the ultrastructure of myocardial tissue in mice were significantly improved in low-, high-dose rutin groups, and the effects were more significant in the high-dose rutin group. Conclusion Rutin could decrease the levels of myocardial enzyme in serum in diabetic mice, improve the cardiac cell morphology and alleviate myocardial injury.