Objective:To observe the protective effect and mechanism of scutellarin（Scu） on hypertrophic cardiomyopathy induced by L-thyroxine（L-Thy） in rats.Method: The rats were randomly divided into six groups: normal group

model group

captopril group（25 mg · kg-1）

Scu-high

medium and low-dose group（100

50

25 mg · kg-1）.Except normal group

rats were treated by ip of L-Thy to establish cardiac hypertophic model and treated with corresponding drugs via ig at the same time.The change of cardiac indexes

the activity of creatine kinase（CK）

lactate dehydrogenase（LDH） and aspartate aminotransferase（AST） in plasma

the content of hydroxproline（Hyp） in left ventricle

morphological changes of cardiac tissue were measured.Result: Compared with normal group

the cardiac indexes

the activity of CK

LDH

AST in plasma

the content of Hyp in left ventricle were significantly increased（P<0.01）;the myocardial hypertrophy and myocardial fibrosis were appeared in model group.Compared with model group

Scu each groups can significantly decreased the left ventricular mass indexes（P<0.05）;Scu each groups can significantly decreased the activity of CK

LDH

AST;Scu high-dose group could significantly decreased the content of Hyp（P<0.05） and markedly inhibited myocardial hypertrophy.Conclusion: Scu could prevent cardiac hypertrophy induced by L-Thy and protect cardiac tissue from injury.