Objective: To assess the relationship between the amount of breastfeeding and late-onset sepsis in very low birth weight infants within 4 weeks after birth.Study Design: In this retrospective study, we analyzed the effect of the breastfeeding ratio of 305 very-low-birth-weight infants on late onset sepsis.Results: The incidence of late-onset sepsis in the high-breastfeeding group, low-breastfeeding group, and the formula-fed group was 0.49% (1/203), 7.41% (6/81), and 4.76% (1/21), respectively (P < 0.05). Single-factor logistic regression analysis showed that, in the low-breastfeeding group, the risk of late-onset sepsis higher than that in the high-breastfeeding group, with an OR value of 16.16 (95% CI: 1.91, 136.47) (P < 0.05). Multivariate logistic regression analysis also confirmed that, compared with the high-breastfeeding group, the low-breastfeeding group had an increased risk of late-onset sepsis, with an OR value of 18.86 (95% CI: 1.91, 136.47) (P < 0.05). Conclusion: The breastfeeding amount of very-low-birth-weight newborns accounting for more than 60% of the total feeding amount within four weeks after birth may reduce the risk of late-onset sepsis.