This study is a prospective, randomized, placebo-double-blind, multicenter clinical trial. The purpose of this study is to investigate whether "butylphthalide +PCI" combined treatment mode on the basis of traditional drug therapy could reduce myocardial infarct size, improve cardiac function and long-term prognosis of patients with acute myocardial infarction, and verify the drug safety of butylphthalide in the treatment of STEMI within the window period of 12 hours.

Inclusion Criteria:

1. Age range of 18-75 years, encompassing both genders;
2. Patients presenting with an initial clinical diagnosis of acute ST-segment elevation myocardial infarction (STEMI), within a maximum time frame of 12 hours from the onset of pain to consideration for trial inclusion, who fulfill the criteria for percutaneous coronary intervention (PCI) and express their intention to undergo PCI;
3. The subject and their legal representative possess the capacity and willingness to provide informed consent by signing.

Exclusion Criteria:

1. Uncontrolled hypertension (systolic blood pressure≥200mmHg and/or diastolic blood pressure≥110mmHg);
2. Previous PCI or CABG;
3. Long-term use of loading doses of anticoagulant or antiplatelet drugs;
4. History of hemorrhagic stroke or ischemic stroke within 6 months, peptic ulcer, prolonged cardiopulmonary resuscitation (more than 10 minutes) within the last 6 weeks, surgery, or major trauma;
5. Known allergy to butylphthalide or excipients;
6. Patients with any of the following conditions: cardiogenic shock, chronic congestive heart failure NYHA class ≥III, severe hypotension, pulmonary insufficiency, severe hepatic and renal insufficiency;
7. History of congenital or acquired hemorrhagic diseases, coagulation factor deficiency diseases, thrombocytopenic diseases, etc. Or any of the following laboratory tests (INR > 2.0, platelet count < 100×109/L, Hb < 10g/dl);
8. Pregnancy, lactation, and planning to become pregnant within 30 days;
9. Severe mental disorder, alcohol dependence or inability to cooperate with informed consent and follow-up due to dementia;
10. Concurrent malignant tumor or severe systemic disease with expected survival time less than 30 days;
11. Have participated in or are currently participating in another clinical intervention study within 30 days before randomization;
12. Other reasons for not being eligible for the study.