OBJECTIVE To evaluate application of recombinant human luteinizing hormone (r-hLH) used in ovarian stimulation of assisted reproductive technique and impact on outcome of pregnancy. METHODS From Apr. to Jul. 2009, 123 patients with low LH level (< 1 U/L) at day 3 of menstruation and down-regulation of pituitary function undergoing in vitro fertilization-embryo transfer (IVF-ET) in Reproductive Medical Center, Provincial Hospital Affiliated to Shandong University were enrolled in this study, whom were classified into 66 cases treated by r-hLH in r-hLH group and 57 cases without r-hLH treatment in non-r-hLH group. In the mean time, 145 patients with normal level of serum LH (1 - 2 U/L) not given by r-hLH treatment and undergoing IVF-ET were matched as control group. Total amount of gonadotropin, estradiol levels and LH levels on the administration of human chorionic gonadotropin (hCG), number of oocytes retrieved, number of 2PN zygotes, rate of high quality embryos, the rates of implantation and clinical pregnancy were compared among these three groups. RESULTS The level of serum LH on the day of hCG administration were (1.59 ± 0.77) U/L in r-hLH group, (0.54 ± 0.25) U/L in non-r-hLH group and (2.39 ± 1.01) U/L in control group, which reached statistical difference between every two groups (P < 0.05). The rates of high quality embryo were 59.36% in r-hLH group, 57.79% in non-r-hLH group, which were significantly lower than 65.94% in control group, respectively (P < 0.05). The rates of 2PN were 67.62% in r-hLH group and 68.32% in control group, which were significantly higher than 62.84% in non-r-hLH group, respectively (P < 0.05). The rates of implantation of 29.77% in r-hLH group were significantly higher than 18.26% in non-r-hLH group (P < 0.05). The total amount of gonadotropin, estradiol level on the day of hCG administration, the number of oocytes retrieved, and clinical pregnancy rate were not significantly different among those three groups (P > 0.05). CONCLUSIONS The administration of recombinant human luteinizing hormone in patients who are profoundly suppressed after down-regulation with long protocol can get more quality embryos, the higher rates of 2PN and implantation.