Lecanemab is a new drug used to treat early Alzheimer's disease (AD) with mild cognitive impairment or mild dementia. It is a human anti-Aβ fibril monoclonal IgG1 antibody, which is injected intravenously into the patient, through the blood-brain barrier into the brain, clearing amyloid plaque, thereby slowing the rate of cognitive decline in patients and delaying disease progression. This article reviews the pharmacological studies, clinical studies, safety and limitations of lecanemab, in order to help clinical understand the current research status and existing achievements of this drug.