Babies cry at night may be related to environmental factors, improper feeding, pinworms and other factors. 1. Environmental factors: because of the infant thermoregulation center is not well developed, the room temperature is too cold or too hot, so that the baby is not comfortable and crying; or room noise, lighting is too strong, etc. will make it difficult for infants to sleep, restless. 2. Improper feeding: infant stomach capacity is small, gastric acid and pepsin secretion is small, such as too much milk, not burp after feeding, supplemental food is difficult to digest and other factors, so that the baby appeared to be bloating discomfort, can lead to crying at night. 3. Pinworms: pinworms are a kind of intestinal parasites, have the characteristic of crawling out of the anus at night to lay eggs, so that the baby sleeps in the anus, perineum itching, can cause babies to cry at night. Babies cry at night may have other reasons, such as calcium deficiency, etc., it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.