Objective:To analyze the correlation between the severity of acute pancreatitis (AP) and the levels of zonulin, zonula occludens protein-1 (ZO-1), tumor necrosis factor -α (TNF -α) in the peripheral blood of patients with acute pancreatitis (AP), and the value of predicting moderate and severe AP.Methods:The clinical data of 115 AP patients admitted to the Second Affiliated Hospital of Anhui Medical University from June 2020 to January 2022 were retrospectively analyzed. They were divided into mild group (69 cases) and moderate severe group (46 cases). The blood levels of zonulin, ZO-1, and TNF-α were measured for all patients on the 1st, 3rd, and 7th day after admission, and the results of the two group tests were compared. The correlation between zonulin, ZO-1, TNF -α and Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) scores on the 1st day was and the value of various indicators for predicting moderate to severe AP were analyzed.Results:The C-reactive protein (CRP) levels of AP patients in the moderate to severe group were higher than those in the mild group, and the difference was statistically significant (all P<0.05). The levels of zonulin, ZO-1, and TNF -α in AP patients in the moderate to severe group showed an upward trend on the 1st, 3rd, and 7th days after admission. The levels of zonulin, ZO-1, and TNF -α in AP patients in the moderate to severe group were higher than those in the mild group at the same time point, and the differences were statistically significant (all P<0.05). The APACHE Ⅱ score of AP patients on the first day of admission was positively correlated with the levels of zonulin, ZO-1, and TNF -α ( r=0.736, 0.552, 0.621, all P<0.05). Zonulin had the highest area under the curve (AUC) for predicting moderate to severe AP, at 0.892, with an optimal threshold of 2.075 pg/ml. Zonulin had the highest sensitivity, at 0.804, and ZO-1 had the highest specificity, at 0.926. Using zonulin ≥2.075 pg/ml, ZO-1≥399.4 ng/ml, and TNF -α≥40.88 pg/ml as thresholds; the sensitivity and specificity obtained from parallel experiments were 0.976 and 0.710, respectively; The sensitivity and specificity obtained from the series of experiments were 0.326 and 0.999, respectively. Conclusions:There is a correlation between the serum levels of zonulin, ZO-1, and TNF -α in AP patients and the severity of AP. Zonulin, ZO-1, and TNF -α have certain clinical value in predicting moderate to severe AP.