Abstract: OBJECTIVE To analyze the relationship between polymorphisms of human leukocyte antigen (HLA) gene, microbial infection of the reproductive tract and recurrent spontaneous abortion (RSA). METHODS The clinical data of 84 patients with RSA admitted to the department of Obstetrics and Gynecology of Dongguan Materal and Child Health Hospital between Jan. 2018 and Jan. 2021 were retrospectively analyzed, the patients were assigned as the RSA group, and another 50 pregnant women who voluntarily underwent abortion in the hospital during the same period were enrolled as the control group. The reproductive tract microorganisms were examined by micro-ecology. The polymorphisms of HLA-G, HLA-C and HLA-DQB1 genes were detected by real-time polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS Chlamydia trachomatis (CT), Ureaplasma urealyticum (UU) and Neisseria gonorrhoeae (NG) were the main infectious pathogens. The positive rates of CT, UU and NG infection in the RSA group were significantly higher than those in the control group. The gene frequency of 14 bp gene heterozygote (+14 bp/-14 bp) in the RSA group was significantly higher than that in the control group (P<0.05), and gene frequency of inserted homozygote (+14 bp/+14 bp) was significantly lower than that in normal control group (P<0.05). The HLA-C1/C2 genotype was significantly dominant in the RSA group (P<0.05), and the dominant genotype in the control group of pregnant women was HLA-C1/C1. The gene frequency of HLA-C gene heterozygote (HLA-C1/C2) in the RSA group was significantly higher than that in the control group (P<0.05), while gene frequency of homozygote (HLA-C1/C1 or HLA-C2/C2) was significantly lower than that in the control group (P<0.05). The frequency of HLA-DQB1*0201 allele in the RSA group was significantly higher than that in the control group, while frequency of HLA-DQB1*0302 allele was significantly lower than that in the control group (P<0.05). There was no significant difference in frequency of the other alleles between the two groups. The genotype frequency of non-asparaginic acid at 57th locus of HLA-DQB1 in the RSA group was significantly higher than that in the control group (P<0.05). CONCLUSION The microbial infection of reproductive tract and polymorphisms of HLA gene were associated with the occurrence of RSA.