NEC is the abbreviation for neonatal necrotizing small intestinal colitis, which occurs mostly in preterm infants and is less common in full-term infants. It is related to immature intestinal development, hypoxia-ischemia and infection in preterm infants, and is one of the complications of prematurity. The main clinical symptoms are abdominal distention, vomiting, diarrhea and bloody stools. The diagnosis mainly relies on clinical symptoms and abdominal X-ray examination. Mild small bowel colitis can be cured by fasting, gastrointestinal decompression and anti-infection treatment in most cases, while severe cases need surgical treatment. Necrotizing small bowel colitis should be detected and diagnosed promptly to avoid serious consequences.