Early antiplatelet therapy is promising for further improvement of functional prognosis on the basis of intravenous thrombolytic therapy. The primary purpose of this multicenter, randomized, double-blind, placebo-parallel controlled trial is to evaluate the efficacy and safety of the early dual antiplatelet therapy (within 6 hours of onset ) of ticagrelor with aspirin combined with intravenous thrombolysis in improving good functional outcome (mRS score 0-1) at 90 days inpatients with ischemic stroke.