Abstract: OBJECTIVE To research the protective effects of Qinxin decoction on CMVECs infected by Coxsackievirus B3 (CVB₃). METHODS CVB₃ RNA were detected by RT-PCR, cells morphology were observed by inverted microscope, cell viability were tested by CCK8 and the best intervention time and concentration of Qinxin decoction were chosen. Then endothelial cells marker-CD31 and mesenchymal cells marker-α-SMA were tested by immunofluorescence and Western blot in optimal conditions. RESULTS CVB₃ could be replicated sustainably in CMVECs. The best intervention time and concentration of Qinxin decoction were 72 h and 20% diluted concentration. Compared with that in the blank group, CD31 protein showed a low expression, but α-SMA showed higher and the cells changed to pyknosis or variation in the group CVB₃. Compared with that in the blank serum group, CD31 protein showed high expression, but α-SMA showed lower and the cells grew quite well in the Qinxin decoction serum group. CONCLUSION Qinxin decoction could inhibit the process of endothelial-to-mesenchymal transition and has a good protective effect on CMVECs following CVB₃ infection.