Alzheimer′s disease (AD), a neurodegenerative disease with high morbidity, wide affection and complex pathogenesis, has become hot spot of scientific researches over the latest forty years. For β amyloid protein, the key protein to AD, and its precursor, amyloid precursor protein (APP), plaque deposition and oligomer were successively hypothesized as the pathogenesis for AD. However, with the development of research technology in recent years, the correlation between β amyloid plaque and β amyloid oligomer has been found, which makes the correlation between the two pathogenesis hypotheses of AD improved. In this paper, we reviewed the research results on the pathogenesis of β amyloid protein and its precursor protein in recent years, compared and analyzed the two hypotheses, and proposed possible directions and hot spots for future research related to the pathogenesis of AD.