Abstract: Yes- associated protein (YAP) is a multifunctional protein that can interact with different transcription factors to acti -vate gene expression. YAP, as the key transcription protein of Hippo pathway, has made important contribution to the control of the or-gan size, stem cell biology, and tissue-specific stem cell self renewal. In the Hippo pathway, MST 1/2 kinases, together with the adaptor protein SAV, phosphorylate LATS 1/2 kinases. YAP is phosphorylated and inhibited by the activated LATS 1/2, a key component of the Hippo tumor suppressor pathway. In recent years, numerous studies have shown that the high expression of YAP in the embryonic stem cells, neural stem cells, and hematopoietic stem cells can maintain the cancer stem cell; and YAP has become the marker of cancer stem cells. Meanwhile, more and more studies indicate that the disorder of Hippo- YAP signaling pathway may be associated with cancer stem cells. In this review, we mainly discuss the role of the Hippo pathway in the stem cell biology and its potential implications in tis -sue homeostasis and cancer.