Abstract: Objective To explore the risk factors of nosocomial infection after chemotherapy in patients with multiple myeloma. Methods Clinical data about 106 patients with multiple myeloma treated in our hospital from January 2017 to March 2019 after chemotherapy were analyzed.The univariate analysis and multivariate regression analysis were carried out to explore the risk factors of infection after chemotherapy. Results Totally 106 cases (58 males and 48 females) with average age of (62.24±9.45) years were included in our study.All patients had received chemotherapy for 172 times,and infection occurred 113 times,with the nosocomial infection rate of 65.70%.The main infection sites included lung and skin.Pathogenic specimens of 113 cases were collected and sent to the laboratory for cultivation,and 90 strains of bacteria were cultured,with positive rate of 79.64%,including 13 strains of Gram-negative bacteria,4 strains of Gram-positive bacteria and 73 undefined strains.Fungal infections occurred in 63 cases,of which 48 had bacteria and fungal infections in lung.Another 8 cases had viral infections,including 7 cases of herpes zoster virus infection and 1 case of cytomegalovirus infection.Multivariate analysis showed that length of hospital stay (≥15 days),high R-ISS stage,use of bortezomib,albumin<35 g/L and neutrophil count<2×10⁹/L were independent risk factors for nosocomial infection in patients with multiple myeloma after chemotherapy (all P<0.05). Conclusion For patients with risk factors such as length of hospital stay ≥15 days,high R-ISS stage,use of bortezomib,albumin<35 g/L,neutrophil count<2×10⁹/L,the occurrence of infection should be monitored and controlled timely.