Objective To explore the expression and role of LAT1 in mouse uterus on early placenta formation on day 8 of pregnancy (D8). Methods One hundred and twenty 6-8-week old SPF female Kunming mice were used in this study. Immunohistochemistry was applied to determine the localization of LAT1 protein in the mouse uterus on D8 of pregnancy. The ectoplacental cones (EPCs) were dissected out from D8.5 uterus, and then cultured in vitro with different concentrations of BCH (2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid, specific antagonist of LAT1) and L-leucine (substrate of LAT1) to determine the role of LAT1 during the EPC attachment and outgrowth. Results LAT1 protein was highly expressed in secondary decidual zone and also positively expressed in the mouse uterus on D8. As a specific antagonist of LAT1, BCH significantly suppressed the ectoplacental cone outgrowth, whereas L-leucine showed no significant effect on it. Conclusions LAT1 is expressed in the mouse uterus during early placenta formation and promotes ectoplacental cone outgrowth, suggesting that LAT1 may promote the trophoblast invasion into maternal decidual tissue, and participates in the early formation of placenta.