Abstract: Human oocyte cryopreservation，as one of the fertility preservation technologies，plays key role in assisted reproductive technology（ART）. Due to the limitation of ethics and research condition，the oocyte cryopreservation technology developed slowly in past decades. With the development of freezing-thawing technology and intracytoplasmic sperm injection (ICSI) in recent years, oocyte cryopreservation has been widely used in clinical practice. The traditional slow freezing method has being gradually replaced by vitrification in most IVF centers, because vitrification has advantages of simplicity，higher oocyte survival rate and less cell damage. There are still the potential risks of cross contamination and cell damage during oocyte cryopreservation process, which can be lowered by the closed vitrification system, vapor storage system, and the sterilized liquid nitrogen with ultraviolet radiation (UV). Compared to slowing freezing, vitrification has advantage in reducing oocyte freezing damage.

Key words: Oocytes, Cryopreservation, Freezing, Fertilization in vitro