Taking aspirin has some effect on preventing blood clots. Aspirin prevents blood clots by inhibiting the appearance of thromboxane A2 for the purpose of inhibiting platelet aggregation. The principle of action is irreversible inhibition of cyclooxygenase to anti-platelet. Clinically, it is widely used in the treatment of cardiovascular and cerebrovascular diseases, especially in patients with secondary prevention of cardiovascular and cerebrovascular diseases, and it can also be used to prevent thrombosis after arterial surgery or intervention. Taking aspirin also has a lot of adverse reactions and side effects, such as nausea, vomiting, epigastric discomfort, stomach pain, a part of the patients with gastric problems will also appear bleeding, such patients should be careful with aspirin. It is contraindicated in patients who are allergic to aspirin, perioperative pain in cardiac bypass surgery, patients with a history of gastrointestinal bleeding or perforation, and patients with severe heart failure. Patients who take aspirin to prevent blood clots should pay attention to the side effects of the drug, and if they can not be relieved, it is recommended to go to the hospital to consult a physician, and should not be used indiscriminately, so as not to aggravate the condition.