Viral myocarditis affects about 5% to 20% of the population. So far, there are not many effective antiviral treatments available. QiHong, the combination of the extracts from Astragali (Huangqi), Rhadiola rosea (Hongjingtian), and Sophora flavescens (Kushen), was developed based on laboratory research. The aim of this study was to investigate the effect and mechanism of QiHong on coxsackievirus B3 (CVB3)-induced myocarditis. The antiviral activity of QiHong in vitro was evaluated on HeLa and Vero cells infected by CVB3. Ribavirin was chosen as positive control. Our results showed that QiHong possessed potent antiviral effects on CVB3 by sodium 3'-[1-(phenylamino-carbonyl)-3, 4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid and plaque-forming assay (50% inhibitory concentrations [IC50] were 7.16 +/- 0.8 microg/ml and 2.63 +/- 0.5 microg/ml, respectively). The 50% cytotoxicity concentration (CC50) was 16-fold higher in QiHong-treated cells than in ribavirin-treated cells. Time course studies demonstrated that the antiviral effect of QiHong was mainly found during 0-4 hrs of infection, and it blocked the attachment and penetration of CVB3 into cells. In vivo 4-week-old male Balb/C mice were used and inoculated intraperitoneally with CVB3 suspension or normal saline. At 48 hrs after inoculation, the infected mice were gavaged with QiHong or ribavirin. On Day 6, myocardial virus titers were significantly lower in the QiHong-treated group than in the viral-infected groups. On Day 14, QiHong significantly ameliorated CVB3-induced myocardium necrosis; on Day 28, QiHong treatment increased survival rate 4-fold compared with CVB3-infected controls (64% vs. 16%; P < 0.05). The results showed that QiHong is a very promising potent antiviral agent with a highly significant favorable effect on survival and pathologic changes in CVB3-induced myocarditis with less toxicity than ribavirin. The antiviral activity of QiHong is at least partially due to an inhibitory effect on virus attachment and penetration.