Some parents mistakenly believe that they can switch to unfortified breast milk or full-term formula after discharge from the hospital. However, it is not known that this nutritional regimen cannot fill the cumulative deficits in energy and protein in the early postnatal period of preterm/low birth weight infants and cannot meet the catch-up growth requirements. Foreign academic institutions such as the American Academy of Pediatrics (AAP), the European Society of Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) and the American Academy of Family Physicians (AAFP) have emphasized the importance of continued nutritional fortification of preterm/low birth weight infants after discharge from the hospital, with the goal of helping preterm/low birth weight infants achieve an ideal nutritional status to meet both their normal and catch-up growth needs. The normal growth trajectory of infants is influenced by genetics and gender, while catch-up growth depends on a variety of factors such as gestational age, birth weight, degree of disease, nutrition during hospitalization and growth status before discharge, and varies greatly among individuals, so the post-discharge nutritional management strategy is individualized. 1. Breast milk for preterm infants: For preterm infants with birth weight > 2000 g and no risk factors for malnutrition, breast milk is still the first choice after discharge. Attention should be paid to the mother’s diet and nutritional balance. 2, breast milk + breast milk fortification (intensive breastfeeding): Currently, the international recommendation is to use breast milk fortification for very low birth weight infants who are exclusively breastfed to ensure their nutritional needs for rapid growth. China’s “preterm / low birth weight infant feeding recommendations” pointed out that gestational age < 34 weeks, birth weight < 2000g preterm infants should be preferred to breastfeeding fortification; breast milk fortification is added when preterm infants tolerate 100ml / (kg・d) after breastfeeding, HMF will be added to breast milk for feeding. Generally, the standard preparation of fortified breast milk can make its caloric density to 80-85kcal/100ml (1kcal=4.184 kJ). Thereafter, the caloric density of breast milk fortification is reduced according to the growth condition, such as half amount of fortification (73kcal/100 m1). Those with unsatisfactory nutritional status evaluated before discharge need to continue breastfeeding fortification until 40 weeks of gestational age. 3.Formula for preterm infants: It should be used in the hospital as early as possible until the body mass of preterm infants reaches 1800-3500 g. Artificially fed very (ultra) low birth weight infants need to be fed until 40 weeks of gestational age; if breastfeeding weight gain is not satisfactory, it can be mixed with formula for preterm infants (formula for preterm infants should not exceed 1/2 of the total daily amount) as a supplement to breast milk. 4, post-discharge formula for preterm infants: Currently, the European Society of Pediatric Gastroenterology, Hepatology and Nutrition believes that the use of this formula should be limited to those born poorly and discharged from the hospital with weight not reaching corrected gestational age weight for preterm infants. It should be used at least until 40 weeks of corrected gestational age or even 3 months of corrected lunar age. The National Association of Family Physicians, on the other hand, has extended its use to 12 months of corrected gestational age. 5.Infant formula: It is suitable for preterm infants with birth weight > 2000g, nearly full term or with satisfactory weight gain after discharge from hospital, artificially fed or as a supplement to breast milk.