Abstract: The expression of cytokeratin in 129 trophoblastic tumors was studied immunohistochemically using an antibody against broad spectrum cytokeratin. The results showed that the positive rate of neoplastic syncytiotrophoblast (ST) ; intermediate trophoblast (IT) and cytotrophoblast (CT) was 100% respectively. The expression of ST showed strong positive, and plasma type; the expression of IT was middle to strong positive,most of IT was plasma type; the expression of CT appeared middle positive, and plasma membrane type. We beliyed that cytokeratin was a sensitive and reliable marker for neoplastic trophoblasts (including metastatic tumor), and had important value for pathological diagnosis, deferred diagnosis and determination of infiltrating range of trophoblastictumors.