Abstract: Objective：To evaluate the protocol of intermittent withdrawal in controlled ovarian hyperstimulation （COH）in high -responders and slow-responders. Methods 院Total 223 high-responders and slow -responders in IVF-ET circles, reviewed from Sep.2009 to Feb.2011, were divided into two groups: 110patients with the intermittent withdrawal protocol and 113 patients without intermittent withdrawal. Embryonicquality，OHSS's incidence，pregnancy rate，and miscarried rate of two groups were compared. Results 院There were significant difference in basalE2，serumE2 on the third and seventh day，serum LH on the seventh day between with and without the intermittent withdrawal protocol group（P＜0.01）. No significant difference（P＞0.05）was found in fertilization，M域ova，2PN，good quality embryos，pregnancy and miscarried rate between two groups，nor the incidence of moderate severe OHSS in high risk patients. Conclusions 院Although the intermittent withdrawalprotocolinhigh-resorponders and slow-responders does not affect the ovular quality and embryonicquality, it reduces the cycle cancellation caused by obtaining no egg or high risk of OHSS，slows down the speed of endometrial development，and gets a better synchronization between endometrim and embryo.

Key words: Ovary, Ovulation induction, Clinical protocols, Fertilization in vitro, Embryo transfer, Oocyte retrieval, Pregnancy rate