The causes of leg pain at night include environmental factors, growing pains, trauma or calcium deficiency. 1. Environmental factors: the indoor temperature is too low at night or parents cover their children too thinly, resulting in children catching a cold, inducing nerve and muscle dysfunction in the legs and manifesting pain symptoms. 2. Growing pains: due to the child’s usual high activity level, the long bones develop too fast, which is not coordinated with the development of local muscles and tendons. 3. Trauma: due to the child’s legs were hit or bumped by external forces during the day, resulting in localized pain symptoms at night, accompanied by redness, swelling or bruising and so on. 4. Calcium deficiency: too little calcium-containing food or chronic gastroenteritis leading to excessive loss of calcium, and may also be due to too little sun exposure, leading to calcium deficiency symptoms, affecting the normal physiological function of the nerves and muscles of the legs. There are other reasons why children cry out for leg pain in bed at night, and it is recommended that parents take their children to the hospital for examination in a timely manner to avoid blind judgment and to ensure the safety of the children.