Objective: To investigate the relations of levels of neutrophil gelatinase associated lipid lipocalin (NGAL) and ghrelin in peripheral blood of patients with the severity of illness of patients with acute pancreatitis (AP). Methods: The clinical data of 199 AP patients treated previously were collected. Of the patients, 103 cases had mild AP (MAP) and 96 cases had severe AP (SAP); 17 cases (8.54%) died during admission. The differences in NGAL and ghrelin levels and other parameters on the first day of admission were compared between patients with different severity of disease and different outcomes, respectively. Results: In patients with SAP, the levels of NGAL, ghrelin, C-reactive protein (CRP), white blood cells (WBC), serum amylase, procalcitonin (PCT), and APACHE II score, Balthazar CT score and BISAP index were significantly increased compared with patients with MAP (all P<0.05); in patients who died during treatment, all the above-mentioned parameters were also significantly higher than those in patients who were cured (all P<0.05). In the 199 patients, the peripheral blood levels of both NGAL and ghrelin had significant correlation with BISAP index (r=0.579 and 0.482, both P<0.05), and their correlation were superior to those of serum amylase, WBC and PCT with BISAP index. Conclusion: The peripheral blood levels of NGAL and ghrelin in AP patients are closely related to the severity of illness of the patients, and their increase may indicate increased risk of poor prognosis of patients.