Objective:To analyze the association between periampullary diverticula (PAD) and the incidence of post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP), and to further classify diverticula types, and explore the impact of different types of diverticula on PEP.Methods:Data of 505 patients who underwent endoscopic retrograde cholangiopancreatography (ERCP) for various reasons in General Hospital of Ningxia Medical University from May 2021 to May 2022 were retrospectively analyzed. Patients were classified into the diverticula group ( n=133) and the non-diverticula group ( n=372) based on the presence of PAD. The diverticula group was subdivided into types Ⅰ ( n=29), Ⅱ ( n=57), Ⅲ ( n=34), Ⅳ ( n=13) according to the Li-Tanaka classification. The incidences of PEP were compared between the diverticula group and the non-diverticula group, as well as among the four subgroups within the diverticula group. Multivariate logistic regression analysis was used to identify the independent risk factors for PEP. Results:There were significant differences in median age (72 years VS 66 years, Z=-4.626, P<0.001), common bile duct stones [80.45% (107/133) VS 59.94% (223/372), χ2=18.191, P<0.001], acute cholangitis [81.20% (108/133) VS 67.10% (231/372), χ2=16.208, P<0.001], malignant biliary stricture [8.27% (11/133) VS 23.39% (87/372), χ2=14.314, P<0.001] and pancreatic malignant diseases [7.52% (10/133) VS 18.55% (69/372), χ2=9.032, P=0.003] between the diverticula group and the non-diverticula group. The incidence of PEP in the diverticula group was significantly higher than that in the non-diverticula group [24.81% (33/133) VS 7.26% (27/372), χ2=28.835, P<0.001]. The incidence of PEP (36.84%,21/57) in type Ⅱ PAD patients was the highest, showing a significant difference compared with that of type Ⅲ [11.76% (4/34), χ2=6.984, P=0.008]. PAD ( OR=5.045, 95% CI: 2.898-11.194, P<0.001) and difficult cannulation ( OR=4.123, 95% CI: 1.968-8.490, P<0.001) were independent risk factors for PEP. In the Li-Tanaka classification, type Ⅰ ( OR=3.055, 95% CI: 1.131-8.251, P=0.028) PAD and type Ⅱ PAD ( OR=6.082, 95% CI: 3.468-13.344, P<0.001) had a higher risk of PEP compared with non-PAD patients. Conclusion:PAD is one of the independent risk factors for PEP. Types Ⅰ and Ⅱ PAD, according to the Li-Tanaka classification, are associated with an elevated risk of PEP when compared with non-PAD patients.