【Abstract】Objective To study the intervention effect and mechanism of paeonol on myocardial fibrosis model rats.Methods By establishing myocardial fibrosis model, 10 rats were randomly divided into model group, low dose paeonol group (10mg kg -1), middle dose paeonol group (15mg kg -1), high dose paeonol group (20mg kg -1), and 10 rats in normal group. The left ventricular enddiastolic pressure (LVEDP), left ventricular systolic pressure (LVSP) and left ventricular index were measured. The pathological changes of myocardium were observed. Collagen volume fraction (CVF) and enzymelinked immunosorbent assay (ELISA) were calculated. Superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatinine inactivating enzyme MB (creat MB) were detected by the attached test. Western blot was used to detect TGFβ1/Smad3 pathwayrelated proteins.Results The left ventricular index, CVF, MDA, LDH, AST and CKMB in low, medium and high dose paeonol group were lower than those in model group, while the levels of LVEDP, LVSP, SOD and CAT were higher than those in model group (P＜005). The left ventricular index, CVF, MDA, LDH, AST and CKMB in highdose paeonol group were lower than those in lowdose paeonol group and middledose paeonol group, while the levels of LVEDP, LVSP, SOD and CAT were higher than those in lowdose paeonol group and middledose paeonol group (P＜005). The expression of TGFβ 1, Smad2 and Smad3 in low, medium and high dose paeonol group were lower than that in model group (P＜005). The expression of TGFβ 1, Smad2 and Smad3 in highdose paeonol group were lower than that in lowdose and middledose paeonol group (P＜005).Conclusion Paeonol can improve the cardiac function of rats by activating the TGFβ1/Smad3 pathway, regulate the levels of oxidative stressrelated factors, and inhibite the development of myocardial fibrosis.