We conducted a prospective, randomized, and controlled trial to assess the optimal dose for GnRH antagonist, cetrorelix, for Chinese women during the course of ovarian stimulation. The patients were randomly divided into two groups, in which 48 patients were advised to inject 0.25 mg Cetrorelix daily (the 0.25 mg group), while 39 patients were instructed to receive a daily dose of 0.125 mg cetrorelix (the 0.125 mg group). In general, a daily dose of 0.125 mg cetrorelix could be more optimal for Chinese women as manifested by the lower cancellation rate, higher implantation rate and clinical pregnancy rate. Specifically, daily administration of 0.125 mg cetrorelix for patients under 35 years old is associated with a 3-fold higher implantation rate and a 5-fold higher clinical pregnancy rate as compared with that of those patients ≥ 35 years old. On the contrary, higher rates for implantation and clinical pregnancy were noted by daily injection of 0.25 mg cetrorelix in elder patients (≥ 35 years old) as compared with that of young patients (< 35 years old). Together, our data suggest that a daily dose of 0.125 mg cetrorelix could be more optimal for patients < 35 years old, while 0.25 mg/day of cetrorelix are likely conducive to higher implantation and clinical pregnancy rate for those patients ≥ 35 years old. These data could be important for preventing LH surge while maintaining optimal LH levels necessary for embryo implantation for Chinese women during the course of IVF-ET treatment.