Background: To assess the effect of these two protocols in patients of different ages. Methods: 1923 in vitro fertilization and embryo transfer (IVF-ET) cycles were divided into two groups: a GnRH-ant protocol group and GnRH-a long protocol group, and then every group were subdivided into four age ranges. The general materials and IVF outcomes were compared. Results: The incidence of OHSS fluctuated from 0% to 2.37% with GnRH-ant protocol, which was significantly lower than another (P P Conclusion: The antagonist protocol should be considered in patients with a high ovarian response (e.g., PCOS patients) to avoid OHSS. Older patients (>35 years) could be treated with the antagonist protocol.