Human cancer stem cells (CSCs) represent promising tools for new approaches to cancer etiology studies and anti-cancer strategy. Because of their distinctive capability to recapitulate the development of the original tumors in vivo, the study of human cancer stem cells largely relies on models of xenograft transplantation into immunodeficient mice. Here we shortly review the knowledge on the concept of CSCs, the relationship between CSCs and tumors,the progress in the xenograft-model studies and the factors influncing the establishment of the CSCs models.