Inadequate feeding, digestive disorders, metabolic diseases and other causes of infant underweight, should be timely to the hospital to clarify the cause of the disease, can be adjusted through the way of feeding, medication and so on to alleviate the underweight situation. 1. Improper feeding: Inadequate feeding may be caused by improper feeding, such as not breastfeeding on demand, resulting in insufficient nutritional intake. Therefore, it is necessary to adjust the feeding method and pay attention to breastfeeding on demand to ensure that the infant’s nutrition is adequate. 2. Indigestion: If the infant is suffering from indigestion due to improper feeding, it may also affect the nutritional intake of the infant, thus causing the infant to be underweight. The use of Saccharomyces boulardii and Bacillus subtilis granules to regulate the intestinal flora can help improve the gastrointestinal function of infants. Meanwhile, pay attention to reasonable feeding. There may also be other reasons for the baby’s weight not reaching the standard, such as certain metabolic diseases, etc., should be timely to the hospital, to clarify the cause of the targeted treatment.