Coughing up black blood clots in esophageal cancer is mainly considered to be caused by tumor invasion, which may also be caused by digestive tract diseases, such as rupture of esophageal varices and peptic ulcer. 1. Tumor invasion: if the patient’s esophageal tumor invades the blood vessels of esophageal wall, it may cause hemoptysis, and whether the hemoptysis is bright red or dark red depends on the amount and speed of bleeding. 2. Rupture of esophageal varices: If the patient has esophageal varices, the blood vessels may rupture after eating cold and hard food, and the patient may cough up black blood clots. 3. Peptic ulcer: most patients may not have obvious symptoms, but some patients may have bleeding at the site of the ulcer, resulting in hemoptysis. Therefore, it is recommended that patients go to the doctor in time to clarify the cause of the disease and get treatment as soon as possible.