The following reasons can be considered in terms of environmental factors: 1, the indoor temperature is too high: the room temperature should preferably not exceed 24 ℃, otherwise the child is prone to sweating, discomfort, irritability and crying. 2, there are irritants in the air: irritants in the bedroom may make the baby’s respiratory tract blocked, and thus crying occurs. Irritants can be the smell of cigarettes, prickly heat powder, mosquito repellent lotion, paint, etc.. 3, sound: when the child is in a light sleep stage, or in the process of entering a light sleep from a deep sleep, any sudden, loud, unfamiliar sound, can wake the child, causing a lot of crying.