Currently, dual antiplatelet therapy with aspirin and clopidogrel (with loading doses) is widely used for patients with acute ischemic stroke. However, immediate, potent and reversible inhibition of platelet aggregation is not possible. Additionally, more than 5% patients have aspirin resistance and more than 15% patients have clopidogrel resistance. Therefore, an intravenously administered GPIIb/IIIa receptor inhibitor (Tirofiban) receptor blocker with fast onset and offset of actions will provide more desired antiplatelet effects in the setting of acute ischemic stroke, especially in patients with high risk of neurological deterioration. This study will measure the anti-platelet effects of Tirofiban in patients with acute ischemic stroke who had high risk of neurological deterioration.

Inclusion Criteria:

1. Acute ischemic stroke with 24 hours of symptom onset.
2. NIHSS≥4 and ≤20 points, and the paralyzed limbs is able to actively move the muscle (standardized motor examination rating scale of 2 or much higher).
3. Age 18-80 years old.
4. Informed consent obtained from patient or acceptable patient's surrogate.

Exclusion Criteria:

1. Treated with intravenous or endovascular thrombectomy for the indexed acute ischemic stroke.
2. Acute ischemic stroke caused by determined or suspected cardioembolism.
3. Acute ischemic stroke caused by other determined caused, including moyamoya disease, artery dissection, arteritis, and etc.
4. Pre-stroke mRS ≥2 or the paralyzed limbs are dyskinesia before stroke.
5. Known hematochezia, gastrointestinal bleeding and any other bleeding.
6. Allergy to tirofiban or its solvents.
7. Patients suffered from severe diseases, including malignant tumor, liver cirrhosis, kidney failure, congestive heart failure, and etc.
8. Gastrointestinal or genitourinary tract bleeding within 1 years.
9. Determined coagulation disorders, platelet dysfunction, or platelet count <100*109/L.
10. Major surgical operation or severe trauma within 1 month.
11. Hemorrhagic retinopathy.
12. Chronic hemodialysis.
13. Uncontrolled hypertension with systolic blood pressure >180 mmHg or diastolic blood pressure >110 mmHg.
14. Acute pericarditis.
15. Other conditions that determined by the investigators.