To explore the expression of GB1 in mouse uterus from day 1 to day 8 of pregnancy (D1～D8) and the role in placenta establishment, semi-quantitative reverse transcription polymerase chain reaction (semi-qRT-PCR), immunohistochemistry and Western blotting were applied to detect the expression levels of GB1 mRNA and protein respectively from D1 to D8. Besides, EPCs and decidual cell were dissected out from D8.5 uterus and then added different concentrations of GABA, GABA B receptor agonists baclofen and antagonists 2-hydroxysaclofen. In vitro attachment and outgrowth assays were performed in EPCs, and transwell chambeer was performed in decidual cells. In vivo, mouse from D8 to D13 were treated by intraperitoneal injection of different concentrations of GABA . On D14, the placenta structure was examined with the histological method. The results suggested that GB1 mRNA and protein dynamic expressed from D1 to D8 uterus. 100 μmol/L GABA and 5 μmol/L baclofen promoted EPCs outgrowth and surppressed decidual cells invasion. At the same time, 20 μmol/L 2-hydroxysaclofen could reversed both of the functions of GABA on EPCs and decidual cells. The histological structures of placentas changed appearantly on D14. In the layer of labrinthine, the cells arranged crowdly and maternal blood and fetal rat vascular decreased number or dysplasia. In spongiotrophoblast, cytotrophoblast cells becomed smaller and glycogen cells decreased or disappeared. The combined results indicated during the early-middle mouse placenta establishment GABA signal was in favour of trophoblasts invasion but played converse role in decidual cells and damaged placenta structure.