The causes of pain on the left side of the stomach are mainly indigestion, gastric ulcer, pancreatitis and so on. 1. Indigestion: it can be caused by a large amount of food, the stomach digestive burden increased, resulting in indigestion, the left side of the stomach pain discomfort after meals, fullness, burning sensation, early satiety, pain in the upper middle abdomen and other symptoms. Usually should pay attention to develop good eating habits, regular diet, avoid overeating. 2. Gastric ulcer: when the ulcer is located in the greater curvature of the stomach, the pain on the left side of the stomach is intense, mostly occurring after eating, caused by gastric acid secretion gastric mucous membrane is strongly stimulated, but also appeared after meals, epigastric dull pain, distension and other symptoms of discomfort. 3. Pancreatitis: related to gallstones, excessive alcohol consumption, smoking, with the left upper abdominal pain is the most common, accompanied by a series of symptoms, such as fever, fatigue, anorexia, weight loss and other symptoms, the symptoms can be aggravated after meals. The symptoms of pain on the left side of the stomach alone cannot accurately determine the cause, but also need to be combined with the characteristics of the medical history, other test results to make an accurate judgment, it is recommended to clarify the cause of the disease under the guidance of a doctor.