• Frequency of adverse events during hospitalization [ Time Frame: 7 days ]
  All adverse events until day-7 or discharge (whichever is earlier)
• Frequency of adverse events during follow-up [ Time Frame: 3 months ]
  Severe adverse events through day-90 after the onset of acute ischemic stroke.

• National Institute of Health stroke scale (NIHSS) at 7 days from onset or discharge [ Time Frame: 7 days ]
  National Institute of Health stroke scale (NIHSS) at 7 days from onset or discharge. Ranged from 0 to 42, a low value represents a better outcome.
• Proportion of patients with Modified Rankin Scale (mRS) Score 0-2 [ Time Frame: 3 months ]
  Proportion of patients with Modified Rankin Scale (mRS) Score 0-2. Ranged from 0 to 6, a low value represents a better outcome.

• Changes of hematological indicators [ Time Frame: 24 hours ]
  Hematological samples are collected at right before thrombolysis and 24 hours after thrombolysis, and changes of hematological indicators related to hemorrhagic transformation (such as Axl, ANGPTL4) are compared between the two groups.
• Changes of the function of dynamic cerebral autoregulation [ Time Frame: 10 days ]
  The function of patients' dynamic cerebral autoregulation are tested 3 times within 10 days from onset and compared between the two groups.

• Device: remote ischemic conditioning
  Remote ischemic conditioning (RIC) is induced by 4 cycles of 5 min of healthy upper limb ischemia followed by 5 min re-perfusion. Limb ischemia was induced by inflation of a blood pressure cuff to 200 mm Hg.
• Device: sham remote ischemic conditioning
  Sham remote ischemic conditioning (RIC) is induced by 4 cycles of 5 min of healthy upper limb ischemia followed by 5 min re-perfusion. Limb ischemia was induced by inflation of a blood pressure cuff to 60 mm Hg.

• Active Comparator: RIC group
  RIC+Standard medical treatment Remote ischemic conditioning (RIC) is induced by 4 cycles of 5 min of healthy upper limb ischemia followed by 5 min re-perfusion. Limb ischemia was induced by inflation of a blood pressure cuff to 200 mm Hg. RIC will be conducted twice within 6 to 24 hours from thrombolysis. Additionally,the patients will be treated with standard medical treatment according to Guidelines for diagnosis and treatment of acute ischemic stroke in China 2014.
  Intervention: Device: remote ischemic conditioning
• Placebo Comparator: control group
  Sham RIC+Standard medical treatment Remote ischemic conditioning (RIC) is induced by 4 cycles of 5 min of healthy upper limb ischemia followed by 5 min re-perfusion. Limb ischemia was induced by inflation of a blood pressure cuff to 60 mm Hg. RIC will be conducted twice twice within 6 to 24 hours from thrombolysis. Additionally,the patients will be treated with standard medical treatment according to Guidelines for diagnosis and treatment of acute ischemic stroke in China 2014
  Intervention: Device: sham remote ischemic conditioning

Inclusion Criteria:

• 1) Age≥18 years, < 80 years, regardless of sex;
• 2) Patients with clinically definite diagnosis of acute ischemic stroke and undergo intravenous thrombolysis;
• 3) Baseline NIHSS >= 5, and <= 25;
• 4) Baseline GCS ≥8;
• 5) Signed and dated informed consent is obtained

Exclusion Criteria:

• 1) Patients who undergo endovascular treatment;
• 2) mRS ≥ 2 before the onset of the disease;
• 3) Double upper limbs or lower limbs paralysis was found in this case;
• 4) Active bleeding of organs within 6 months of admission or current, including cerebral hemorrhage, subarachnoid hemorrhage, gastrointestinal hemorrhage, fundus hemorrhage and so on;
• 5) Other intracranial lesions, such as cerebrovascular malformation cerebral venous diseases, tumor and other diseases involving the brain;
• 6) Concurrent use of anticoagulation drugs including Warfarin, dabigatran, rivaroxaban;
• 7) Severe organ dysfunction or failure;
• 8) Patients suffering from severe hematological diseases or severe coagulation disorder dysfunction
• 9) Those who have a history of severe trauma or had major surgery within 6 months prior to admission;
• 10) Those who have a history of atrial fibrillation;
• 11) The patients who have the contraindication of remote ischemic conditioning treatment, such as severe soft tissue injury, fracture or vascular injury in the upper limb#Acute or subacute venous thrombosis, arterial occlusive disease, subclavian steal syndrome, etc;
• 12) Pregnant or lactating women;
• 13) Previous remote ischemic conditioning therapy or similar treatment;
• 14) Patients with a life expectancy of less than 3 months or patients unable to complete the study for other reasons;
• 15) Severe hepatic and renal dysfunction;
• 16) Unwilling to be followed up or treated for poor compliance;
• 17) He/She is participating in other clinical research or has participated in other clinical research or has participated in this study within 3 months prior to admission;
• 18) Other conditions that the researchers think are not suitable for the group.