Objective:To study on mechanisms of Shenbai Injectio in regulating myocardial myosin heavy chain（α-MHC）gene expression in viral myocarditis.Methods:The ventricutar muscle of nascent Wistar rats aged 1-3 days was separated and taken aseptically for preparation and culture of myocadial cells to establish viral myocarditis infection model——in vitro cultured myocardial cells of the rat infected Coxsackie virus B3（CVB3）.And the effect of Shenbai Injection on α-MHC gene expression was detected with immunohistochemical methods.Results:The obvious positive sign of α-MHC gene expression could be seen in the normal group

and it decreased in the virus infection group

and it was significantly up-regulated in the virus infection plus Shenbai Injectio group.Conclusion:Shenbai injectio can relieve autoimmune injury to reduce the probability of changes of MHC phenotype with ATPase activity

so as to up-regulate expression of α-MHC and strength myocardial contractility.