The endometrial implantation window is the period of time during which the uterine lining allows the embryo to implant, usually around day 20-24 of the normal menstrual cycle and lasts for about 24 hours, and it is this 24 hours that is crucial for the implantation of the embryo. However, due to individual differences, the implantation window may be advanced, delayed or shortened in about 25% of women. Therefore, it is very important to accurately recognize when the endometrial implantation window opens in order to improve the success rate. Failure to grasp the endometrial implantation window is one of the most important factors for embryo implantation failure. In the face of repeated embryo implantation failures, doctors and patients should not be in a hurry to achieve success, but should first learn about the individualized embryo implantation window through a variety of methods and adjust the endometrial lining to the optimal state before embryo transfer in order to obtain a better clinical outcome. The success rate of a single fresh or thawed cycle at the First Hospital of Lanzhou University Specialized Hospital for Reproductive Medicine is stable at more than 60%, and the total pregnancy rate after one fresh cycle and two thawed cycles can reach 80%-90%. Then for about 10-20% of patients with repeated implantation failures, our hospital has set up the Repeated Implantation Failure Difficulties Group. The research team combines international and domestic cutting-edge information, and the success rate of re-transplantation of patients facing pre-treatment, accurate regulation and grasping of the opening of the implantation window, has reached more than 50%, and we have gained experience in difficult cases and repeated implantation failures. After years of accumulation, the results are remarkable, and there are constantly good news!