Objectives: Research suggests the efficacy of progesterone for luteal phase support in assisted reproduction cycles using gonadotropin-releasing hormone analogues. Our study objective was to compare the efficacy of two available preparations of progesterone, vaginal gel and intramuscular injection, for luteal phase support in assisted reproduction cycles. Study design: This study included data gathered from 18 reproductive centers in China. Subjects were randomly allocated to receive progesterone gel or intramuscular progesterone (IMP). The progesterone gel group received micronized progesterone in gel (8%, 90 mg)once daily; the IMP group received IMP (progesterone oil)once daily. The ongoing pregnancy rate was calculated (number of women with a viable pregnancy at 12 weeks divided by the number of women who had undergone an oocyte pickup cycle). Results: A total of 1313 patients were enrolled in the study, 1248 of whom began treatment. The intention-to-treat set included 527 and 531 patients in the gel and IMP groups, respectively. The ongoing pregnancy rate in the progesterone gel group was non-inferior to that in the IMP group (48.4% [95% confidence interval (CI): 44.0, 52.8]vs. 46.3% [95% CI: 42.0, 50.7]); the between-group rate difference was 2.1% (−4.0, 8.1). There was no difference between the gel group and IMP group on most secondary endpoints, including implantation rate, biochemical pregnancy rate, clinical pregnancy rate, multiple pregnancy rate, early abortion rate, and vaginal bleeding rate, but there was a between-group difference in luteal phase bleeding rate. The safety analysis showed no difference in the incidence of total adverse events. Conclusions: Progesterone gel showed good efficacy and safety outcomes and therefore provides an alternative method of luteal support in Chinese in vitro fertilization patients. © 2019 Elsevier B.V.