Angiotensin converting enzyme inhibitor (ACEI) is an important type of antihypertensive drug. Much evidence shows that ACEI not only decreases the blood pressure but also has the protective effect on the cardiac and cerebral vessels. ACEI may prevent the stroke. To provide the best evidence for the clinical practice, we electronically searched RCTs and systematic reviews from MEDLINE and The Cochrane Library to evaluate the mechanisms and the effects of ACEI in stroke treatment and prevention.