Abstract: Objectives: To investigate the regulatory mechanism of miR-451a on human villous trophoblast invasion. Methods：Human chorionic villus trophoblast cell line HTR-8/SVneo was transfected with synthetic oligonucleotide miR-451a mimics. Reverse transcription-real-time PCR was used to detect the expression of miR-451a and the expression of MIF mRNA. The expression of MIF protein in transfected cells was detected by Western Blot. Transwell cell invasion assay was used to observe the changes of cell invasiveness before and after transfection. The recombinant human macrophage migration inhibitory factor (rhMIF) and ISO-1，the Specific inhibitors of MIF ，were added to HTR-8/SVneo cells. The expression of E-cadherin protein and Vimentin protein in cells was detected by Western Blot. Results：The miR-451a expression in HTR-8/SVneo cells transfected with miR-451a mimics was significantly increased, the expression of MIF mRNA and protein was decreased, and the cell invasive ability was decreased. Compared with the blank group, E-cadherin protein expression decreased and Vimentin protein expression increased in rhMIF group.The expression of E-cadherin protein expression increased and Vimentin protein expression decreased in ISO-1 group. Conclusion: Transfection of miR-451a down-regulates the expression of MIF in human extravillous trophoblast cells and may regulate the invasion ability of human villous trophoblast cells through the epithelial-mesenchymal transition pathway.