Objective:To explore the predictive value of neutrophil to albumin ratio (NAR) in patients with severe acute pancreatitis (SAP) complicated with abdominal infection.Methods:The clinical data of 93 SAP patients admitted to Shunyi Teaching Hospital, Capital Medical University from January 2020 to December 2022 were retrospectively analyzed. According to the incidence of abdominal infection during hospitalization, the patients were divided into infection group (21 cases) and non-infection group (72 cases). The general data, first laboratory examination indexes and NAR values within 24 h after admission were collected and compared between the two groups. Logistic regression was used to analyze the influencing factors of abdominal infection in SAP patients. The predictive value of NAR for abdominal infection in SAP patients was analyzed by receiver operating characteristic (ROC) curve.Results:The number of organ failure in the infection group was higher than that in the non-infection group: 2.00 (1.00, 2.00) vs.1.00 (1.00, 2.00), with a statistical significant difference ( P<0.05). The levels of neutrophil (NEU), C-reactive protein and NAR in the infection group were higher than those in the non-infection group: (10.18 ± 1.26) × 10 8/L vs. (9.43 ± 1.13) × 10 8/L, (16.75 ± 2.27) mg/L vs. (15.16 ± 2.41) mg/L, (3.62 ± 0.63) × 10 8/g vs. (3.11 ± 0.47) × 10 8/g, and the level of albumin was lower than that in the non-infection group: (28.45 ± 3.16) g/L vs. (30.57 ± 2.94) g/L, with a statistical significant difference ( P<0.05). Logistic regression analysis showed that a large number of organ failure, high levels of NEU, C-reactive protein and NAR were risk factors for abdominal infection in SAP patients ( OR>1, P<0.05). The low level of Alb was the protective factor of abdominal infection in SAP patients ( OR<1, P<0.05). The ROC curve analysis showed that NAR predicted the area under curve of SAP patients complicated with abdominal infection to be 0.74, which has certain predictive value. Conclusions:NAR is associated with abdominal infection in SAP patients, and can assist clinical early prediction of the risk of abdominal infection.