Pain below the left rib cage may be caused by angina pectoris, pericarditis, pleurisy, lung cancer, intercostal neuritis, trauma and so on. 1. Angina pectoris: atherosclerotic lesions of the coronary arteries of the heart lead to local narrowing, when strenuous exercise, emotional excitement, etc. lead to an increase in the oxygen consumption of the myocardium, myocardium further ischemia and hypoxia and angina pectoris, so the left side of the ribs below the chest area of the location of the pain. 2. Pericarditis: after inflammatory lesions occur in the pericardium, the connective tissue attached to the surface of the heart, the exudation increases, resulting in the formation of pericardial effusion and pain in the left chest area. 3. Pleurisy: Inflammatory exudation, adhesion, hemorrhage and other lesions appear after pleural infection, which involve the left pleura and lead to pain below the left rib cage, and may be accompanied by systemic symptoms such as fever and fatigue. 4. Lung cancer: Lung cancer in middle or late stage invades the chest wall and stimulates the nerves of the left chest wall, resulting in pain below the left rib cage. 5. Intercostal neuritis: left intercostal nerve trauma, infection and other factors lead to inflammatory lesions, resulting in radiating stabbing pain at the lower edge of the left rib cage along the rib cage. 6. Trauma: the left side of the rib cage is violently impacted, extrusion and other traumatic injuries leading to rib fractures, chest cavity tissue damage, and thus the left side of the rib cage below the pain. The pain below the left rib cage may be related to many factors, and it is recommended to consult a doctor for a clear diagnosis.