To analyze the relationship between MTHFR gene polymorphism of infertility patients with endometriosis and their efficacy of assisted reproduction. Methods: The clinical data of 107 infertile patients with endometriosis (in observation group) and 109 infertile patients with simple fallopian tube problems (in control group) from January 2016 to December 2019 were collected retrospectively. The patients in both groups were treated with vitro fertilization and embryo transfer (IVFET). The gene polymorphism of MTHFR of the patients in the two groups was detected. The therapeutic effect and pregnancy outcomes of IVF-ET of the patients with different genotypes were analyzed. Results:The proportions of heterozygous mutants (CT) and homozygous mutants (TT) at MTHFR677 site of the patients in the observation group were significantly higher than those of the patients in the control group, while the proportion of wild type (CC) at MTHFR677 site of the patients in the observation group was significantly lower (P<0.05). In the observation group, the dosage of Gn used of the patients with TT genotype was significantly higher than that of the patients with CC genotype or CT genotype during IVF-ET treatment, and the number of eggs in M Ⅱstage, the fertilization rate, and the high-quality embryo rate of the patients with TT genotype were significantly lower. The incidence of adverse pregnancy outcomes (28.6%) of the patients with TT genotype was significantly higher than that (9.1%) of the patients with CC genotype or that (12.5%) of the patients with CT genotype (P<0.05). Conclusion: The clinical effect of IVF-ET for treating infertility patients with endometriosis and TT mutation of MTHFR gene is not good, and the adverse pregnancy outcomes of these patients is easy to occur, which should be paid more attention to in clinic.