Small children running stomach pain on the left side, may be caused by intestinal spasm, may also be suffering from intestinal diseases. 1. When children run, the gastrointestinal peristalsis will be accelerated, easy to induce intestinal spasm and cause left-sided abdominal pain; coupled with the redistribution of blood circulation during running, the gastrointestinal blood flow will be correspondingly reduced, resulting in the intestinal blood supply is relatively insufficient to cause abdominal pain on the left side of these cases in the rest, abdominal pain will be alleviated on its own. 2. If the child suffers from intestinal diseases, such as intestinal polyps, enteritis, etc., when running due to increased intestinal peristalsis and induced left-sided abdominal pain symptoms. Children running stomach pain on the left side, there may also 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.