Currently, the guideline recommended re-perfusion such as intravenous thrombolysis and mechanical thrombectomy as the most effective treatment for acute ischemic stroke. However, the two methods are restricted by a strict time window, which greatly limits the number of the patients receiving treatment. The abundant studies have suggested that good collateral circulation can provide compensatory blood supply to save the ischemic penumbra and reduces the infarct volume, which improves the prognosis. How to improve collateral circulation in an efficient and safe way is a clinical challenge. Our recent experiment results of the animal and preliminary clinical experiments show that head-down position may significantly increase cerebral perfusion and improve neurological function. Clinically, head-down position is simple and easy to operate, and theoretically may increases brain perfusion and improve collateral circulation. A pilot randomized clinical trial is designed to investigate the effect of head-down position combined with routine rehabilitation in patients with ischemic stroke.The study is designed to explore the efficacy and safety of head-down position in patients with acute ischemic stroke

Inclusion Criteria:

1. Patient age over 18 years
2. acute ischemic stroke within 24 h of onset
3. neurological deficit: 6≤NIHSS≤16
4. Large artery atherosclerosis etiology based on TOAST typing
5. the supplied vessel is the middle cerebral artery or internal carotid artery, and the degree of stenosis was more than 50%.
6. first stroke onset or past stroke without obvious neurological deficit (mRS≤1)
7. Signed informed consent

Exclusion Criteria:

1. Disturbance of consciousness
2. Hemorrhagic stroke or mixed stroke
3. Combining with severe organ dysfunction
4. Past hemorrhagic stroke
5. A history of stroke with severe sequelae
6. Planned revascularization within 3 months
7. Ischemic stroke due to surgical intervention
8. participating in other clinical trials within 3 months
9. Pregnant or lactating women
10. any inappropriate patient assessed by the researcher