Oxidative stress has been proposed to be an important factor in the pathogenesis of Alzheimer's disease (AD) and contributed to β-amyloid (Aβ) generation. Interaction between oxidative stress and neuro-inflammation leads to Aβ generation. AD is associated with an increase in blood-brain barrier (BBB) permeability due to tight junction involvement. Oxidative stress decreases the expression of low-density lipoprotein receptor-related protein 1 and up-regulates receptor for advanced glycation end products in BBB and increases the BBB permeability, which could potentially lead to increased deposition of Aβ within AD brain. Apoptosis takes place in the pathogenesis of AD, and oxidative stress contributes to apoptosis through both extrinsic pathway and intrinsic pathway. Oxidative stress-induced apoptosis may be a potential factor to Aβ generation. Aβ generation requires two sequential cleavages of APP, with the two proteolytic enzymes: β-secretase and γ-secretase. Oxidative damage up-regulates Aβ via inducing activity of β- and γ-secretases. In this review, we will focus on the mechanism and pathway that oxidative stress contributes to Aβ generation.