Abstract: The blood vessels and the immature cellular clusters surrounded them in uterine leiomyomas or fetal uterine muscle layers have been obversed with H-E Staining, Gomori's reticulin staining and immunohistochemistry in which marked endothelial cells of blood vessels. It has been concluded that the endothelial cell can not differentiated into the cells of leiomyomas, the new-growth muscle cells of blood vessel walls in leiomyomas have the same origin with leiomyoma cells, and uterine leiomyoma cells are originated from the undifferentiated messenchamal cells.