The mechanism of thrombus formation in living vessel wall is complex and involves a combination of blood and vessel wall properties and local flow conditions. The significance, theory and experimental techniques of thrombus formation in vivo were comprehensively reviewed. Particularly, the important role of signaling pathway and hemodynamic in thrombus formation in vivo was pointed out. The difficulty in in vivo animal models was analyzed. Some recent new phenomena as well as new approaches and directions worthy of investigation also were summarized.