Most patients with coronary heart disease take aspirin, which is a very important drug as a cornerstone drug for secondary prevention of coronary heart disease. However, some patients who take aspirin develop gastrointestinal bleeding or even gastrointestinal hemorrhage and hemorrhagic shock. Here we remind all patients, especially those with underlying gastric and duodenal diseases, to take aspirin must pay attention to the protection of gastric mucosa and acid-suppressing drugs. Commonly used drugs to protect the gastric mucosa such as aluminum thioglycollate, acid suppressants such as omeprazole, lansoprazole, etc. During taking aspirin, pay attention to any acid reflux, epigastric pain, etc. Pay attention to the color and shape of stools and any black stools. The correct understanding and use of aspirin is necessary to achieve the important therapeutic effect of the drug and avoid its side effects.