Abstract: OBJECTIVE To explore the etiological characteristics of postoperative infection in breast cancer patients undergoing mastectomy and analyze the association with gene polymorphisms of Toll-like receptor 4（TLR4） and stimulator of interferon gene（STING） 1. METHODS Totally 125 breast cancer patients who received mastectomy in Shangrao Maternal and Child Health Hospital from Jun 2019 to Jun 2021 were enrolled in the study, the clinical data of the patients were retrospectively analyzed, the patients were divided into the infection group with 9 cases and the no infection group with 116 case according to the status of postoperative infection. The sites of postoperative infection, distribution of pathogens and gene polymorphisms of TLR4 and STING1 were observed. RESULTS Totally 9（7.2%） patients had postoperative infection. The respiratory tract and surgical incision were the major infection sites. A total of 17 strains of pathogens were isolated, 11（64.71%） of which were gram-negative bacteria, and 5（29.41%） were gram-positive bacteria; Pseudomonas aeruginosa was the predominant species of the gram-negative bacteria; Staphylococcus aureus was dominant among the gram-positive bacteria. The frequency of GA genotype at rs27371909 locus of TLR4 gene was higher in the infection group than in the no infection group（P＜0.05）. There were no significant differences in the frequencies of GG, AA genotypes and alleles at rs27371909 locus of TLR4 gene and genotypes and alleles at rs10116253 locus between the two groups of patients. There was significant difference in the frequency of alleles at rs1131769 of STING1 between the two groups of patients, however, there were no significant differences in the frequencies of genotypes at rs1131769 locus of STING1 and the frequencies of genotypes and alleles at rs7380272. There were no significant differences in the gene interactions at the loci of TLR4 and STING1. CONCLUSION The breast cancer patients undergoing mastectomy are still at high risk of postoperative infection, and the patients carrying with GA genotype at rs27371909 locus of TLR4 gene are at higher risk of infection. The gram-negative bacteria are dominant among the pathogens. The respiratory tract and surgical incision are the common infection sites.