Abstract: Objective To investigate the expression of human leucocyte antigen protein G (HLA-G) in different trophoblast cells and different stages of pregnancy. Methods The expression of HLA-G protein in normal placenta and trophoblasts of different trimesters was detected using immunohistochemical method (SP). Results HLA-G protein expression exhibited spatio-temporal changes, which located in the extravillous trophoblast (EVT) and was higher in the placenta of the first and second trimesters while lower in the third trimester (P<0.01). Conclusion HLA-G protein expression in different stages of pregnancy and different trophoblasts may be related to the controlled invasion of the trophoblast.