Abstract: OBJECTIVE To explore the relationship between vitamin D receptor (VDR) gene polymorphisms and infection in multiple myeloma (MM) patients after chemotherapy. METHODS From May 2017 to May 2021, totally 30 MM patients who had nosocomial infection in the Second Affiliated Hospital of Chengdu Medical College during chemotherapy were assigned as the infection group, meanwhile, 48 patients who did not have nosocomial infection were chosen as the non-infection group.The distribution of pathogens was analyzed, the genes at rs7975232 and rs1544410 loci of VDR were detected by polymerase-chain-reaction-restriction-fragment-length polymorphism (PCR-RFLP) assay.Multivariate logistic regression analysis was performed for influencing factors for the infection in the MM patients after chemotherapy. RESULTS Totally 46 strains of pathogens were isolated from the 30 patients with infection, 56.52% of which were gram-negative bacteria.The frequency of C allele at rs7975232 locus of VDR gene was higher in the infection group than in the non-infection group(P＜0.05).Granulocytopenia(OR=1.533) and hypoproteinemia(OR=1.608) were the independent influencing factors for the infection in the MM patients after chemotherapy (P＜0.05). CONCLUSION The MM patients are at high risk of infection after chemotherapy.The gram-negative bacteria are dominant among the pathogens causing the infection.The infection may be associated with the gene mutation at rs7975232 locus of VDR.The granulocytopenia and hypoproteinemia are the influencing factors for the infection in the MM patients after chemotherapy.