The success rate of blastocyst transfer is around 40%-50%. There are many factors that affect blastocyst transfer, such as endometrial thickness, endocrine hormone level, blastocyst quality, etc. It is important to have good quality blastocysts for blastocyst transfer. The basis of good blastocysts is good sperm and eggs, and pregnancy preparation is also very crucial to improve the success rate of blastocyst transfer. Multiple blastocysts are grown and the doctor selects the better quality blastocysts for in vivo transfer. The development of embryos requires a good in vivo environment, which is introduced as follows: i. A suitable thickness of endometrium is needed, the thickness of endometrium is more than 10mm suitable for embryo implantation, if the endometrium is too thin or suffering from inflammation of endometrium, it will affect the normal implantation of embryos leading to transfer failure. Secondly, blastocyst transfer needs good hormone level in the body as support, if the progesterone and other hormone values in the body are low, it will also affect the success rate of blastocyst transfer.