Objective To study the mechanism of protective function of Donglian component [compatibility of 麦冬（Radix Ophiopogonis polysaccharide） with 黄连 （Rhizoma Coptidis alkaloid）] on the myocardium tissue of diabetic rats.Methods Healthy male SD rats were made models of diabetes by abdominal injection of streptozotocin（STZ） buffer solution.The successful model rats were randomized into model group

metformin group（0.188g/kg）

Donglian small-dose group（1.35g/kg） and large-dose group（6.75g/kg）

with 10 in each.Ten healthy rats were normal control.From the second day of modeling

the metformin and Donglian component were made fluid of the specific concentration and same volume were administered by gavage

and the normal group and model group were given the same volume distilled water by gavage

for 4 weeks in succession.Weight of the heart

left ventricle/body weight index

the content of myocardium angiotensin Ⅱ（AngⅡ） and endothelin（ET）

and the expression of receptor of angiotensin converting enzyme（ACE） in myocardium were determined.Results Compared with the modle group

the heart weight

left ventricle/body weight index

and contents of AngⅡ and ET in Donglian large-dose group were significantly decreased（P<0.05

P<0.01） and the expression of ACE receptor was inhibited. Conclusion Donglian component protects the myocardium of diabetic rats through inhibiting the expression of ACE receptor and decreasing the contents of AngⅡ and ET.