This study examined the effect of MMP9 gene on the biological behaviors of trophoblasts and explore the relation between MMP9 gene and the "superficial implantation of placenta".In vitro cultured trophoblasts (TEV-1 cells) were transfected with synthesized double-stranded MMP9 RNA (siRNA) by using lipofectamine2000TM technique and the expressions of MMP9 mRNA and protein and the growth and invasiveness of the TEV-1 cells were determined.Our results showed that siRNA transfection could significantly inhibit the expression of MMP9 gene in the TEV-1 cells and the growth and invasiveness of the TEV-1 cells transfected RNA was significantly reduced (P＜0.01).We are led to conclude that silencing of MMP9 gene with siRNA can inhibit the growth and invasiveness of trophoblasts and increasing the expression of MMP9 might help prevent and treat preeclampsia.