The purpose of this study is to assess the effectiveness and safety of Qingre Huatan formula versus placebo on preventing early neurological deterioration in patients with acute ischemic stroke within 48 hours after onset.

Inclusion Criteria:

1. Inpatients diagnosed with acute ischemic stroke. Inpatients diagnosed of acute ischemic stroke.
2. Meet the criteria of TCM phlegm-heat syndrome
3. Patients at high-risk of END : Magnetic resonance imaging (MRI) reveals new ischemic lesions, with DWI-ASPECTS score ≤ 7, or presence of at least two risk factors of END.
4. Acute ischemic stroke within 48 hours after onset.
5. Aged 18-80 years, male or female.
6. The patient or representative has signed informed consent.

Exclusion Criteria:

1. Received or planned thrombolysis or endovascular therapy after onset.
2. Suspected secondary stroke caused by brain tumor, brain trauma, hemopathy, etc.
3. Already dependent in activities of daily living before the present acute stroke (defined as modified Rankin Scare score ≥2 )
4. Diseases that cause motor dysfunction, including osteoarthritis, etc.
5. Known severe liver or kidney dysfunction (alanine aminotransferase or aspartate transaminase > 2 times the upper limit of normal value, serum creatinine > 1.5 times the upper limit of normal value)
6. Known severe aphasia or mental illness affecting clinical information collection and evaluation.
7. Pregnancy, potential pregnancy or breastfeeding.
8. Currently participating in other clinical trials.