Objective：This study aims to investigate the effects of gestational diabetes mellitus（GDM）on the expression and methylation status of PGC-1α and PDX1 in placenta，and to explore the correlation between PGC-1α，PDX1 and fetal blood glucose. Methods：The birth weight and placental weight of 30 pregnant women with GDM were collected. The corresponding data of 30 full-term neonates without pregnancy complications and umbilical cord abnormalities were collected as control group. DNA and RNA were isolated from placental trophoblast tissue immediately after delivery. The DNA methylation levels of the PGC-1α and PDX1 genes were quantitatively detected using sodium bisulfite sequencing. PGC-1α and PDX1 mRNA levels were measured by reverse transcription quantitative PCR（qRT-PCR）. At the same time，placental insulin，blood glucose and HbA1c levels were detected. Results：Fetal birth weight and placental weight were significantly higher in the GDM group than those in the control group（P < 0.05）. Insulin，HbA1c and blood glucose levels were significantly higher in the GDM group than those in the control group（P < 0.01）. Cord blood insulin levels were positively correlated with birth weight（r=0.648，P < 0.001），placental weight（r=0.795，P < 0.001），blood glucose（r=0.862，P < 0.001），and HbA1c（r=0.927，P < 0.001）. The levels of PGC-1α and PDX1 mRNA were lower in the GDM group compared with the control group，and the PGC-1α gene methylation level was higher in the GDM group than that in the control group（P < 0.05）. There was a negative correlation between blood glucose and mRNA expression of PGC-1α （r=-0.438，P=0.002） and PDX1（r=-0.373，P=0.007） in the placenta. Conclusion：The changes of epigenetic modification of PGC-1α gene in pregnant women with GDM may be one of the causes of abnormal glucose metabolism in their offspring.