Objective: To investigate the ultrasonographic features of solid pseudo papillary tumor of the pancreas (SPTP) and pancreatic ductal adenocarcinoma(PDAC), to initially screen and compare the key points of ultrasonographic diagnosis between the two. Methods: The ultrasound findings of 48 patients with SPTP and 48 patients with PDAC confirmed by surgical pathology in our hospital from August 2009 to March 2018 were retrospectively analyzed. Their ultrasound sonographic features and the key points for differentiation between them were summarized. Results: Using pathological findings as the gold standard, the coincidence rates of the ultrasound diagnosis of SPTP and PDAC was 68.8%(33/48) and 85.4%(41/48), respectively. On ultrasound images, the origin of the mass, internal echogenicity, calcification and internal blood flow were very similar to those of PDAC (P>0.05). However, the rate of clear margins, regular morphology and liquefaction were significantly higher in SPTP than those in PDAC[SPTP, 73.9%(34/46), 73.9%(34/46) and 37.0%(15/42);PDAC, 28.6%(12/42), 35.7%(15/42) and 7.1%（3/42）, whereas the incidence of dilatation of the main pancreatic duct was lower in SPTP than that in PDAC 6.5%(3/46) vs. 35.7%（15/42）, with a statistically significant difference (P<0.01). Among the above ultrasound features, the liquefaction feature was the most significant criterion for identifying SPTP and PDAC. Conclusion: The use of ultrasound screening to identify SPTP and PDAC has the advantages of being non-invasive, convenient and economical. SPTP should be considered first when ultrasound shows a pancreatic mass with liquefaction in a clear margin and regular shape.