Objective：To investigate the expression of phosphatidylinotidol 3-kinase/protein kinase B（PI3k/Akt） signal pathway，matrix metalloproteinase-2（MMP-2） and matrix metalloproteinase-9（MMP-9） in villi tissues of normal pregnancy and spontaneous abortion and their relationship. Methods：Real-time PCR，immunohistochemistry and Western blot were used to detect the expression and location of PI3k，Akt，p-Akt，PTEN，MMP-2，MMP-9 between normal artificial abortion（20 cases） and spontaneous abortion（20 cases） in villi tissues. Results：The mRNA expression of PI3k（P=0.000），Akt（P=0.005） and MMP-9（P=0.000） in the villi tissues was higher in normal artificial abortion（NOR group） than in spontaneous abortion（SPO group）. The mRNA expression of PTEN in the villi tissues was higher in SPO group than in NOR group（P=0.000）. The protein expression of PI3k（P=0.006），Akt（P=0.000），p-Akt（P=0.000） and MMP-9（P=0.000） in the villi tissues was higher in NOP group than in SPO group. The protein expression of PTEN was higher in SPO group than in NOR group（P=0.000）. MMP-2 had no significant change between two groups（P=0.092）. Western blot results were consistent with the immunohistochemical results. PI3k（P=0.047），Akt（P=0.011），p-Akt（P=0.001），MMP-2（P=0.893） and MMP-9（P=0.005）. Conclusion：PI3k/Akt signal pathway is involved in the spontaneous abortion during the first trimester，which may affect the expression of MMP-9 and reduce the invasion of tropholast. This study provides new evidence for clinical preven－tion and treatment of early abortion.