Alzheimer’s disease (AD) is a neurodegenerative disorders characterized by impaired memory and cognitive functions. The pathogenesis of AD is very complicated, it is extensively documented that the accumulation of β-amyloid peptide (Aβ) is a vital contributing factor in the pathology of AD. Aβ can be divided into different forms of species, such as monomer, oligomer, and fibril. Increasing evidence suggests that oligomeric Aβ, may be the main mediators which contribute to the cognitive deficits and neurodegeneration in AD. The oligomeric Aβ has different aggregation configuration, which play different roles in the process of AD. This review mainly illustrates the role and underlying mechanisms of differently aggregated components of oligomeric Aβ in the progress of AD.