Abstract: Objective: To investigate CT and MRI features of acute peripancreatic fluid collection (APFC), acute necrotic collection (ANC), pancreatic pseudocyst (PPC) and walled-off necrosis (WON) complicating acute pancreatitis. Methods: The image data and clinical data of 64 patients with local complications of first-onset acute pancreatitis from January 2010 to June 2016 were retrospectively analyzed. The location, number, CT density, MR signal intensity, contents, communication with main pancreatic duct or not, infection or not of the lesions were recorded. Results: In this group 21 patients with PPC had total 31 PPC lesions, 12 of 31 lesions located at the lesser omental sac, and there were no necrotic materials in the PPC. Of the 21 patients with PPC, 13 had clinically conservative treatment and 8 had surgery. There were total 43 patients with WON. The WON lesions had communication with pancreatic duct in 11 cases and accompanying infection with "bubble signs" in 5 cases. Adipose tissue and non-liquid contents without contrast enhancement on CT and MRI were found in these WON lesions. Of the 43 patients with WON, 21 patients had clinically conservative treatment and 22 had surgery. The lesions of APFC and ANC were visualized on CT and MRI in early stage of AP disease (within 2 weeks) and the diagnoses were not difficult. Conclusion: CT and MRI were of great value for identifying and diagnosing the local complications of AP. CT showed bubble and fat globules more intuitively, whereas MRI was more sensitive to detect little debris component and fat globules in the lesions.