Accumulation of small soluble oligomers of amyloid-beta (A beta) in the human brain is thought to play an important pathological role in Alzheimer's disease. The interaction of these A beta oligomers with cell membrane and other artificial surfaces is important for the understanding of A beta aggregation and toxicity mechanisms. Here, we present a series of exploratory molecular dynamics (MD) simulations to study the early adsorption and conformational change of A beta oligomers from dimer to hexamer on three different self-assembled monolayers (SAMs) terminated with CH(3), OH, and COOH groups. Within the time scale of MD simulations, the conformation, orientation, and adsorption of A beta oligomers on the SAMs is determined by complex interplay among the size of oligomers, the surface chemistry of the SAMs, and the structure and dynamics of interfacial waters. Energetic analysis of A beta adsorption on the SAMs reveals that A beta adsorption on the SAMs is a net outcome of different competitions between dominant hydrophobic A beta-CH(3)-SAM interactions and weak CH(3)-SAM-water interactions, between dominant electrostatic A beta-COOH-SAM interactions and strong COOH-SAM-water interactions, and between comparable hydrophobic and electrostatic A beta-OH-SAM interactions and strong OH-SAM-water interactions. Atomic force microscopy images also confirm that all of three SAMs can induce the adsorption and polymerization of A beta oligomers. Structural analysis of A beta oligomers on the SAMs shows a dramatic increase in structural stability and beta-sheet content from dimer to trimer, suggesting that A beta trimer could act as seeds for A beta polymerization on the SAMs. This work provides atomic-level understanding of A beta peptides at interface.