Abstract: OBJECTIVE To investigate the serum human neutrophil lipocalin (HNL), interleukin 6 (IL-6) and procalcitonin (PCT) levels before and after continuous blood purification (CBP) in patients with intra-abdominal infection (IAI) and their predictive value for prognosis. METHODS A total of 84 patients who were admitted to the ICU from Jan. 2020 to Jun. 2022 and required CBP treatment were selected as the research subjects.According to scores of Acute Physiology and Chronic Health Evaluation System II (APACHE II), patients were divided into mild to moderate group (APACHE II score >10 points, 50 cases) and severe group (APACHE II score ≤10 points, 37 cases).The clinical data of the included subjects were collected and summarized.At admission and 3d after treatment, levels of serum HNL, IL-6 and PCT were detected.The 28 d prognosis was followed up.The predictive value of serum HNL, IL-6 and PCT for prognosis was evaluated by receiver operating characteristic (ROC) curves. RESULTS The levels of serum HNL, IL-6 and PCT of patients at 3 d after treatment were decreased compared with those at admission (P＜0.05).Serum HNL, IL-6 and PCT in the mild to moderate group before and after treatment were lower than those in the severe group (P＜0.05).All the 87 patients were followed up, 16 patients with poor prognosis and 71 patients with good prognosis.Serum HNL, IL-6 and PCT in the poor prognosis group before and after treatment were lower than those in the good prognosis group (P＜0.05).The AUC values of serum HNL, IL-6 and PCT at 3 d after treatment for 28 d prognosis prediction in IAI patients were 0.730, 0.706, and 0.685, respectively. CONCLUSION Serum HNL, IL-6 and PCT significantly decreased in IAI patients after CBP, and monitoring the above indexes had positive significance for disease and prognosis assessment.