The CCK-8 assay was used to detect the effect of different concentrations of dihydrotanshinone Ⅰ（DiⅠ） on the viability of Vero and IPEC-J2 cells to study the inhibitory effect of DiⅠ on porcine epidemic diarrhea virus（PEDV） in vitro. Methods including real-time fluorescence quantitative PCR（RT-qPCR）， Western blot， indirect immunofluorescence， and virus titer assay were used to evaluate the anti PEDV activity of DiⅠ. The effects of different administration methods on the replication of PEDV were investigated. Molecular docking method was used to evaluate the interaction between DiⅠ and PEDV M^pro. The results showed that DiⅠ had no significant toxicity to Vero and IPEC-J2 cells at the concentrations used in subsequent experiments. DiⅠ significantly inhibited the gene expression and protein synthesis of PEDV in a dose-dependent manner. Full-treatment， co-treatment， and post-treatment all significantly inhibited the replication of PEDV. It is indicated that DiⅠ has anti PEDV activity and can exert inhibitory effects on key stages including invasion， replication， and release of PEDV， making it a potential candidate drug against PEDV infection.