Abstract：【Objective】To observe the dynamic changes of serum LH levels in different GnRH-along protocols，and investigate the relationship between GnRH-adosage and LH levels，and compare the clinical outcomes among different GnRH-a long protocols. 【Methods】In this retrospective study，1.0 mg，0.8 mg，0.375 mg long-acting and 0.1 mg/d，0.05 mg/d short-acting GnRH-a long protocols were included from January to June in 2015 at the Reproductive Medicine Center of the First Affiliated Hospital of Sun Yat- Sen University. Serum LH levels were evaluated from a total of 250 women at the four time points，on the day before gonadotropin stimulation（Gn0），the fourth day of Gn stimulation（Gn4），the seventh day of Gn stimulation（Gn7），and the HCG administration day（HCG day），then the relationship between serum LH levels and the dosage of GnRH-a were analyzed. The number of oocytes retrieved，fertilization rate，good quality embryos rate，blastocyst transferred rate，the number of transferred embryos，implantation rate and clinical pregnancy rate were also compared.【Results】Among the long-acting groups，LH levels in 0.375 mg group werehigher than those in 1.0 mg and 0.8 mg groups at the four time points（P < 0.05）. Total Gn dose，duration of Gnstimualtion and HMG dosage of 1.0 mg protocol and 0.8 mg protocol were significantly higher than those of 0.375 mg group（P < 0.05）. In addition，the implantation rate showed an increasing tendency when the level of LH increases（P > 0.05）. In short-acting groups，the LH levels in 0.05 mg/d protocol were significantly lower than those in the 0.1 mg/d group at Gn0

Gn7 and HCG day（P < 0.05）. Total Gn dose，du? ration of Gn stimulation and HMG dosage did not show significant difference between 0.05mg and 0.1mg group. What′s more，the im? plantation rate in 0.1 mg/d group was higher than in 0.05 mg/d group（P > 0.05）.【Conclusion】Among the long-acting groups，the smaller amount of GnRH-a was administrated，the higher LH levels during ovarian stimulation and implantation rate the patients ob? tained. As to the short-acting groups，the LH level and implantation rate in 0.1 mg/d group is higher than those in 0.05 mg/d group.