Clopidogrel and aspirin are both anti-platelet aggregation drugs, but they have different mechanisms of action. Clopidogrel inhibits platelets by inhibiting the ADP receptor on the platelet surface to prevent thrombosis. Aspirin inhibits platelets by inhibiting the production of cyclooxygenase. Aspirin is actually an organic acid that produces an irreversible inhibition of platelet aggregation. Aspirin is currently the most widely used antiplatelet drug in clinical practice and is the basic drug for cardiovascular diseases. Aspirin can cause damage to the gastric mucosa by direct penetration or stimulate the gastrointestinal tract indirectly by inhibiting the production of prostaglandins. Therefore, aspirin has more side effects than clopidogrel in the gastrointestinal tract. For the side effects of aspirin, such as abdominal pain and diarrhea are more pronounced than clopidogrel. Compared with aspirin, clopidogrel has strong anti-platelet effect and fast onset of action. Therefore, long-term use of clopidogrel is safer than aspirin, but aspirin and clopidogrel can be used in combination to prevent thrombosis after surgery, because the effect of one drug may not be sufficient or reach the antiplatelet effect. In fact, aspirin was first discovered as an analgesic and anti-inflammatory drug, and can be used in small doses to prevent thrombosis and in large doses to relieve fever and analgesia.