The left side of the stomach exhibits significant pain during inspiration, and the following diseases are considered: first, the occurrence of diseases of the thoracic cavity, especially pleurisy combined with infection of the left lower lung. As the disease evolves, there can also be significant localized exudation, which means that a pleural effusion is formed. Patients may experience localized pain, worsened by deep breathing, and in severe cases, restricted breathing. The diagnosis can be confirmed by CT examination of the chest, and after timely and effective intravenous anti-infection treatment, the patient’s symptoms can gradually improve. Second, diseases occurring in the abdominal cavity, especially in the left upper abdomen, gastritis or gastric ulcer, the patient will also have localized pain, which is aggravated after eating. The pain can also be triggered after a full meal, activity, or deep breathing, and there is usually significant acid reflux, belching, and burning sensation in the upper abdomen. The patient’s symptoms can gradually improve with the timely administration of drugs to suppress stomach acid and protect the mucosa of the gastrointestinal tract at the time of onset.