After more than 40 years, IVF technology has made rapid progress. However, the clinical pregnancy rate remained around 33.8-42.7%. After the implementation of blastocyst transplantation, the clinical pregnancy rate increased to 60.4%. One of the key factors affecting the pregnancy rate of IVF is the RIF, actually the poor endometrial receptivity is the main reason for the decrease of pregnancy possibility in RIF patients. In our study, the endometriumof IVF-ET patients during WOI was collected and divided into RIF group and pregnant controls group according to pregnancy outcomes. Specific proteins related to endometrial receptivity were screened by iTRAQ-2D LC-MS/MS.