Ischemic stroke has a variety of treatments and currently drug therapy is one of the main treatments.A number of clinical studies have proved that alprostadil (PGE1) has pharmacological effects of significant dilation of blood vessels, inhibition of plate aggregation, anti-atherosclerosis and increased cerebral blood flow.Evaluate the 90-days efficacy by comparing two groups of patients'(one with alprostadil,another with placebo) mRS.

Inclusion Criteria:

1. ischemic stroke diagnosed by CT or MRI
2. Age: 18-75 years
3. Pre-stroke mRS score is 0-1
4. within 72 hours symptoms onset
5. 4 ≤ NIHSS <20
6. Patient is willing to participate voluntarily and to sign a written patient informed consent

Exclusion Criteria:

1. intracranial tumors, encephalitis or lesions diagnosed by CT or MRI
2. patients with thrombolytic therapy
3. low platelet , blood system diseases or other bleeding tendency
4. suspected subarachnoid hemorrhage or aortic dissection coma
5. atrial fibrillation, myocardial infarction, heart valve disease, infective endocarditis, heart rate <50 beats / min
6. ALT or AST continued to rise more than 3 times the upper limit of normal creatinine clearance rate<30ml/min
7. Dementia and mental illness
8. Patient who is participating in other trials or has been participated in other trials in recent 3 months