OBJECTIVE： To study the effects of Astragalus granules on the expression of Caveolin-3 （Cav-3） and Smad family member 3 （Smad3） in the myocardial cells of rats with viral myocarditis. METHODS： 90 rats were randomly divided into a normal group， a model group， a Shenmai injection group [positive drug， 0.2 g/（kg·d）] and the groups of low， medium and high-dose Astragalus granules [0.42， 0.84， 1.68 g/（kg·d）]， with 15 rats in each group. The rats in all groups except for the normal group were given CVB3 ip for the establishment of viral myocarditis model. Meanwhile， the rats in the drug administration groups were given corresponding drugs ig， while those in the normal group and the model group were given normal saline ig， for 15 consecutive days. 5 rats were selected from each group respectively on the 3rd， 9th and 15th days of drug use to take an experiment. For the rats， the pathological change of the cardiac muscle tissue was observed and scored， and the mRNA and protein expression of Cav-3 and Smad3 in the myocardial cells were detected. RESULTS： After 15 days of drug use， compared to the normal group， the rats of the model group had hyperplasia of a large number of cardiac muscle fibers， obvious lesions at cardiac muscle fibers，  and significantly higher pathological score and levels of the mRNA and protein expression of Cav-3 and Smad3 in the myocardial cells （P＜0.05）. Compared to the model group， the rats in the drug administration groups had cardiac muscle tissue lesions improved and had obviously lower pathological score and levels of the mRNA and protein expression of Cav-3 and Smad3 in the myocardial cells （P＜0.05）. CONCLUSIONS： Astragalus granules can markedly downregulate the gene expression of Cav-3 and Smad3 in the myocardial cells of rats with viral myocarditis， which is inferred as a prevention and treatment mechanism of viral myocarditis.