Objective: To explore the application value of abdominal ultrasonography and abdominal X-ray in assisting diagnosis and predicting clinical outcome of necrotizing enterocolitis (NEC) of newborn. Methods: 80 children with NEC who were admitted to our hospital from February 2015 to February 2019 were retrospectively selected. According to the revised Bell-NEC classification standard, the children were divided into suspected group (39 cases), confirmed group (41 cases), which were divided into good group (improved after conservative treatment in internal medicine, 50 cases) and bad group (operation or death, 30 cases) according to the clinical outcome. All patients were examined by X-ray and ultrasonography. The detection results of two kinds of imaging examination in the suspected group and the confirmed group were collected, and the differences of two kinds of imaging examination in the patients with different clinical outcomes were compared. The value of abdominal X-ray and abdominal ultrasound in predicting the clinical outcome of children with NEC were analyzed. Results: The detection rate of abdominal ultrasonography for intestinal dilatation and portal vein gas accumulation in the diagnosis group were 58.54%（24/41）, 36.59%（15/41），which were higher than those in the suspected group with 36.59%（15/41）, 17.07%（7/41） (P < 0.05). The detection rate of abdominal free gas, intestinal wall gas, portal vein gas and intestinal dilatation detected by abdominal X-ray in the bad group were 13.33%（4/30）, 16.67%（5/30）, 20.00%（6/30）, 50.00%（15/30）, which were higher than those in the good group with 2.00%（1/50）, 2.00%（1/50）, 2.00%（1/50）, 24.00%（12/50） (P < 0.05), and the detection rate of abdominal free gas, peritoneal effusion, intestinal wall thickening and intestinal dilatation detected by abdominal ultrasonography were 16.67%（5/30）, 50.00%（15/30）, 40.00%（12/30）, 50.00%（15/30）, which were higher than those in the good group with 2.00%（1/50）, 24.00%（12/50）, 14.00%（7/50）, 32.00%（16/50）(P < 0.05). The results of logistic regression analysis showed that abdominal free gas, ascites and thickening of intestinal wall were detected by abdominal ultrasound, and intestinal dilatation and free gas detected by abdominal X-ray film were the risk factors of poor clinical outcome of children with NEC (P < 0.05). The results also showed that the sensitivity and specificity of abdominal ultrasonography and X-ray plain film were 83.33%, 63.33% and 78.00%, 72.00% respectively. Conclusion: Compared with abdominal X-ray plain film, abdominal ultrasound has a higher detection rate for intestinal dilatation and portal vein gas accumulation in children with NEC, and can detect the subtle changes in the intestinal tract of children with NEC, which has more application value in assist diagnosis and clinical prognosis of ultrasonic signs of NEC.