Stat3，one of the members of STATs (signal transduction and activators of transcription), activated by polypeptide ligand such as cytokin and growth factors, plays an important role in early embryonic development, epithelial cell apoptosis, skin remodeling and keratinocyte migration et al. The progress in study of Stat3 shows that Stat3 can be constantly activated in many kinds of tumor cell lines; constantly activated Stat3 can make cell malignant transformation happened and repress apoptosis. Study of Stat3 as an oncogene, sets an important basis for explanation of oncogenesis and screening the therapy medicine of many kinds of tumor.