Objective: To review the ultrasonographic characteristics and causes of severe acute pancreatitis (SAP) in children. Methods: The ultrasonographic findings and clinical data of 65 children with SAP that was confirmed by clinical diagnosis or autopsy were retrospectively analyzed. Results: Ultrasonographic manifestations of SAP in children were demonstrated as follows: the pancreases were enlarged to varying degrees, or even to an abnormal shape, with irregular or ill-defined margins; the echo patterns of the pancreas were diverse which included hyperechogenicity, hypoechogenicity or heterogeneous echogenicity; fluid collections in the peripancreatic space and spaces in the abdominal cavity as well as pseudocyst formation were frequently seen; the pancreas of primary SAP presented an abnormal shape and diffuse swelling, with heterogeneous or decreased but no increased echogenicity, and was frequently associated with pseudocyst formation; in secondary SAP, with exception of traumatic SAP, the pancreas had no abnormal shape but showed the presence of localized swelling , with enhanced but no decreased echogenicity, and was not complicated by pseudocyst formation. Among the 65 children, the csuse of SAP was trauma in 28 cases (43.1%), infections in 18 cases (27.6%), idiopathy in 15 cases (23.2%), systemic non-infectious diseases in 3 cases (4.6%), and post-operative stress response in 1 case (1.5%). Conclusion: Ultrasonography can accurately find the imaging changes of the pancreas in children with SAP, which can help make an early diagnosis and judgment of its causes, and thereby effectively reduce the mortality in these children.