Objective: To investigate the role of YAP in ovarian cancer stem cells and its influence on biologic function. Methods: A single cell suspension was prepared after digestion of pancreatic enzymes with OVCAR-3 cells. And then, the ovarian cancer stem cells were identified by flow cytometry. The YAP five phosphorylation site mutation (YAP-5SA) and C terminal deletion (YAP-△C) in the construction of vector lentiviral packaging vector, and the virus core particles transfected with YAP-5SA, YAP-△C vector in ovarian cancer stem cells, then the cell proliferation and stability were examined by MTT assay and colony-forming assay. The ovarian cancer stem cells, YAP-5SA and YAP-△C transfected ovarian cancer stem cells were inoculated in 15 the nude mice, the volume of tumors were measurand for 4 weeks, once a week. Results: After the ovarian cancer stem cells inoculated in DMEM culture medium for 24 h, the number of cells were increased, and 5 days the cells presenting stem cell globules and covering the bottom of the bottle. And the cells had 99.8% CD44 and 0.76% CD117 examined by flow cytometry. YAP level was higher in ovarian cancer stem cells than ovarian cancer cells. And YAP-5SA promoted stem cell proliferation and tablet cell cloning in ovarian cancer stem cells, however, YAP-△C showed the opposite phenomenon. YAP-5SA transfected ovarian cancer stem cells promoted the growth of the tumor, however, YAP-△C transfected ovarian cancer stem cells suppressed the growth of the tumor. Conclusion: These results suggest that YAP contribute to the proliferation of ovarian stem cells and participate in the development and progression of ovarian cancer.