Objective To investigate the clinical utility of ultrasound parameters in diagnosing neonatal annular pancreas. Methods A total of 56 neonates with descending duodenal obstruction underwent saline?contrast ultrasound examination. Ultrasonic parameters， including dilated duodenum diameter （DDD）， dilated duodenum thickness （DDT）， and stenosis duodenum diameter （SDD）， were measured. The cases were categorized into three groups： annular pancreas （group A， n = 28）， descending duodenal atresia （group B， n = 3）， and descending duodenal septum （group C， n = 25）. One?way ANOVA was employed to compare statistical differences among the three ultrasonic parameters across the groups， followed by LSD?t test for pairwise comparisons between two groups showing significant differences. Receiver operating characteristics analysis was conducted to calculate the area under the curve and determine the cut?off value if there were statistically significant differences observed. Results In group A， group B， group C， the diameters of DDD were measured as（23.2 ± 2.4）mm， （25 ± 1.0）mm， （19.4 ± 2.6）mm， respectively. When comparing these three groups， there was a statistically significant difference between group A or group B and group C in terms of DDD diameter measurements （t = 5.7， P < 0.05； t = 3.793， P < 0.05）. However， no statistically significant difference was observed between group A and group B for DDD diameter measurements （t = 1.232， P > 0.05）. The corresponding values for DDT were measured as （3.0 ± 0.6）mm， （3.2 ± 0.4） mm，and（2.4 ± 0.3） mm，respectively. When comparing these three groups，the results showed a statistically significant difference between either Group A or Group B compared to Group C in terms of DDT measurement （t = 4.695， P < 0.05； t = 2.778， P < 0.05）. However，no statistically significant difference was found between Group A and Group B regarding the measurement of DDT （t = 0.666， P > 0.05）. The SDD measurements in the three groups were （1.9 ± 0.3） mm， （3.6 ± 0.8）mm， （5.5 ± 0.7）mm， respectively. Statistical analysis using LSD?t test revealed significant differences between the three groups （t = 5.521， P < 0.05； t = 6.142， P < 0.05； t = 25.828， P < 0.05）.The sensitivity， specificity， positive predictive value， and negative predictive value for detecting annular pancreas at a cutoff of 2.3 mm were determined to be 96.4%， 100%， 100%， and 96.6%， respectively， with an area under the receiver operating characteristic curve of 0.999. Conclusion SDD could be employed for the diagnosis of neonatal annular pancreas.