Abstract: Objective To investigate the effects of laboratory factors on patients with recurrent implantation failure(RIF). Methods Clinical data of 57 cases of RIF in vitro fertilization or intracytoplasmic sperm injection(IVF/ICSI)during 2017 and 2021 were retrospectively analyzed. After the failure of the 3rd embryo transfer, patients who were pregnant after the 4th or 5th embryo transfer were divided into the pregnant group(group A, n=24)and non-pregnant group(group B, n=33). The laboratory and clinical factors of the two groups were compared with independent sample t test, rank sum test and Logistic regression. Results There was statistically significant difference in the number of embryos transferred between groups A and B(1.67±0.48 vs. 1.36±0.49, P=0.024). However, there were no significant differences in baseline data, clinical factors, and embryo scores(P>0.05); there were no significant differences in the transfer of embryos at different developmental stages(cleavage embryo, blastocyst), ovum insemination methods(IVF/ICSI), and the cumulative number of available embryos(P>0.05). Further analysis of the number of transplants from the first to the last cycle indicated that transfer of two blastocysts helped improve the pregnancy outcomes. Conclusion For patients with RIF, transfer of two embryos will improve the success rate of pregnancy.