Objective · To synthesize 4EDB, the derivative of sinomenine, and to observe its therapeutic effects on mice with experimental autoimmune myocarditis (EAM). Methods · The BALB/c mice were randomly divided into three groups: control group, EAM group and EAM+4EDB group with 6 mice in each group, and then treated with 4EDB [5 mg/(kg·d)] by intragastric administration from the 14th day of immunization until sacrificed on the 21th day. Hematoxylin-eosin (H-E) staining was used to identify the areas of inflammation, and the hematoxylin-picrosirius red staining was used to detect the degree of myocardial fibrosis. The expression levels of related inflammatory factors including IL-1, IL-6, IL-17A and TGF-β in myocardial tissues were detected by real-time PCR. Results · Compared with EAM group, the pathological score of myocardial inflammation decreased in EAM+4EDB group (P=0.020), with myocardial fibrosis alleviated, and the expression levels of inflammatory cytokines including IL-1, IL-6, IL-17A and TGF-β in myocardium reduced (P<0.05). Conclusion · The new derivative of sinomenine, 4EDB, can alleviate the myocarditis in EAM mice, and the inhibition of inflammatory factors may play an important role.