Abstract： Objective To investigate the effect of fosinopril on transforming growth factor-β1 (TGF-β1) expression in myocardial tissue of streptozotocin(STZ)-induced diatetic rats. Methods A total of 30 SD rats were enrolled in the study, 10 of them were set as normal controls, others were created the model of diabetes by injecting STZ, and then equally divided into fosinopril group and untreated group. Myocardial TGF-ft was observed in all three groups after 5 weeks. Results The expression of TGF-fi, in myocardial tissue was weakly positive in normal group, strongly positive in untreated group and positive in fosinopriol treat group, with absorbance being 0. 009 ± 0. 004,0. 198 ±0. 007 and 0. 104 ± 0. 005,respectively. Conclusion Fosinopril may partly suppress the increased TGF-β1 expression in myocardial tissue of diatetic rats. It may decrease significantly the myocardial injury of diabetic rats.