The goal of this clinical trial is to compare the effectiveness between early and late initiation of anticoagulation therapy in acute ischemic stroke (AIS) patients with non-valvular atrial fibrillation (NVAF). Participants will be 1:1 randomized into early or late initiation group. The primary endpoint is early neurological deterioration (END) before discharge.

Anticoagulation therapy is effective to prevent ischemic stroke in patients with NVAF who have a history of stroke. Recent clinical trials have demonstrated that early initiation of anticoagulation therapy after AIS is safe, while no remarkable benefits have been observed. The goal of this clinical trial is to compare the effectiveness between early and late initiation of anticoagulation therapy in AIS patients with non-NVAF. Participants will be 1:1 randomized into early or late initiation group. The primary endpoint is END before discharge.

Inclusion Criteria:

• Age > 18 years old
• Acute ischemic stroke with onset < 48 hours
• Have a history or newly diagnosed as NVAF
• NIHSS on admission <= 8

Exclusion Criteria:

• Chronic renal dysfunction (GFR < 30ml/min) or severe hepatic injury
• Have a history or newly diagnosed as valvular heart disease
• Mural thrombus in heart
• Contraindications of anticoagulation therapy within 12 days after AIS, e.g. severe intracranial hemorrhage
• Received reperfusion therapy, e.g. intravenous thrombolysis and endovascular treatment
• Concomitant stenosis (>50%) of carotid artery/intracranial artery, of which the ischemic lesion located within the territory
• Life expectancy less than 1 year
• Plan to receive invasive surgery in the following 3 months and have high risk of uncontrollable bleeding
• Pregnant or lactating women
• Individuals identified by researchers as unsuitable for participation in the study due to other reasons.