Children wake up crying in the middle of the night may be caused by environmental discomfort, nightmares, rickets and other reasons. 1. Environmental discomfort: when sleeping, if the temperature of the environment is too low or too high, mosquito bites, the surrounding sound is too loud, etc. may lead to children waking up crying in the middle of the night. Parents can improve the environment, after a period of time the child will fall back to sleep, no need to worry. 2. Nightmares: If a child has a scary nightmare in his sleep, he may look scared, wake up and cry. Parents can give the child a certain amount of appeasement, usually no special treatment. 3. Rickets: generally caused by vitamin D deficiency, is a common disease in children, the child may appear irritable, night terrors, bone deformity softening and so on. Children wake up crying in the middle of the night if frequent occurrence, it is recommended to take the child for medical treatment, under the guidance of the doctor.