Abstract: Alzheimer's disease (AD) is a common type of dementia that leads to a gradual decline in patients' cognitive abilities, ultimately resulting in the loss of independent living capacity. The complement system, consisting of the classical pathway, the lectin pathway, and the alternative pathway, is an essential component of the innate immune system and plays a significant role in the development of the nervous system and the onset and progression of neurodegenerative diseases. The role of the complement system in AD is complex and multifaceted, with its activation process closely associated with neuroinflammation, neurodegeneration, and cognitive decline in AD. In the early stages of the disease, the complement system may regulate inflammatory responses and exert neuroprotective effects, whereas in the late stages, it may participate in the pathogenesis of AD by promoting inflammatory responses and neurodegenerative changes. This article reviewed the clinical research progress of complement components and their activation products in AD, providing new research and diagnostic directions for AD treatment.