Leg cramps in children may be caused by strenuous exercise, poor sleeping posture, calcium deficiency and other reasons. 1. Strenuous exercise: it may be due to children running a lot, jumping and so on cause the body overwork, produce a lot of lactic acid in the leg accumulation, resulting in leg muscle spasm, leg cramps. 2. Poor sleeping posture: it may be due to continuous lying on the side, curling legs, etc., which presses the leg muscles and the blood circulation is not smooth, which may cause passive contracture and leg cramps. 3. Calcium deficiency: it may be caused by insufficient calcium absorption, insufficient intake, excessive discharge, etc. It can lead to increased nerve excitability, causing muscle contraction and leg cramps. Children’s leg cramps, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.