The adsorption and aggregation of the amyloid-beta (A beta) peptides on the cell membrane plays a causal role in the pathogenesis of Alzheimer's disease. Here, we report all-atom molecular dynamics (MD) simulations study the interactions of A beta oligomer with self-assembled monolayers (SAMs) terminated with hydrophobic CH3 and hydrophilic OH function groups, with particular interests in how surface chemistry and A beta orientation affect the adsorption behavior of A beta. Simulation results show that the CH3-SAM fills a stronger binding affinity to A beta than the OH-SAM does, although both surfaces can induce A beta adsorption. Regardless of the characteristics of the surface, the hydrophobic C-terminal region is more likely to be adsorbed on the SAW indicating a preferential orientation and interface for A beta adsorption. Structural and energetic comparison among six A beta-SAM systems further reveals that A beta orientation, SAM surface hydrophobicity, and interfacial waters all determine A beta adsorption behavior on the surface, highlighting the importance of hydrophobic interactions at the interface. This work may provide parallel insights into the interactions of A beta with lipid bilayers.