Abstract: In order to investigate the effects of surfactin（YUAN.0S and FHYB201030S, produced by the original strain YUAN.0 and the mutant strain FHYB2030, respectively） on Porcine epidemic diarrhea virus（PEDV） and Porcine reproductive and respiratory syndrome virus（PRRSV）, in this experiment the CCK-8 kit was used to detect the toxicity of YUAN.0S and FHYB201030S on African green monkey kidney（Vero） cells and monkey embryonic kidney epithelial（Marc-145） cells. Meanwhile, the direct inactivation, adsorption blocking and replication blocking effects of different mass concentrations of surfactin on PEDV and PRRSV were also examined. The results showed that the maximum non-toxic mass concentration of YUAN.0S in Vero and Marc-145 cells was 7.81 mg/L, while the maximum non-toxic mass concentration of FHYB201030S was increased to 62.50 mg/L. YUAN.0S had essentially no inhibitory effect on PEDV and PRRSV, while FHYB201030S showed some direct inactivation to PEDV and PRRSV; 3.91-62.50 mg/L FHYB201030S could effectively improve the cell viability of PRRSV-infected cells. In addition, in terms of inhibiting virus adsorption and replication, only 62.50 mg/L FHYB201030S could effectively inhibit the adsorption of PRRSV to Marc-145 cells. The results suggested that compound mutagenesis could improve the inhibition effect of surfactin produced by Bacillus subtilis on PRRSV to some extent.