Objective To study the effect of first-week breastfeeding volume on necrotizing enterocolitis (NEC) and feeding intolerance in very low/extremely /extremely-low birth weight neonates. Methods A total of 270 cases of very low/extremely low birth weight neonates were retrospectively reviewed and divided into 3 groups according to the proportion of breast milk feeding in total feeding volume: the >60% group, the ≤60% group, and the all-formula group. The effect of breastfeeding on NEC and feeding intolerance in the first week in the 3 groups was explored. Results Logistic regression analysis showed that the incidence rates of NEC in the ≤60% group ［OR=13.455（95％CI 1.718, 105.343）］,and the all-formula group［OR=19.425（95％CI2.317, 162.845）］ were significantly higher than the >60% group （P＜0.05，P＜0.01）; the incidence rates of feeding intolerance in the ≤60% group ［10.976（95％CI 4.605, 26.163）］, and the all-formula group ［OR=9.876（95％CI 3.688, 26.595）］ were significantly higher than the >60% group （P＜0.01 for all）. Conclusion High breastfeeding proportion within the first week after birth can reduce the incidence rates of feeding intolerance and NEC in very low/extremely low birth weight neonates.