Deposition of amyloid-beta (A beta) aggregates in the brain is a main pathological hallmark of Alzheimer's disease (AD), so inhibition of A beta aggregation has been considered as a promising strategy for AD prevention and treatment. Black phosphorus (BP) is a 2D nanomaterial with high biocompatibility and unique biodegradability, but its potential application in biomedicine suffers from the rapid degradability and unfunctionability. To overcome the drawbacks and broaden its application, we have herein designed an A beta inhibitor (LK7)-coupled and polyethylene glycol (PEG)-stabilized BP-based nanosystem. The PEGylated-LK7-BP nanosheets (PEG-LK7@BP) not only exhibited a good stability but also demonstrated a significantly enhanced inhibitory potency on A beta(42) fibrillogenesis in comparison with its counterparts. This elaborately designed PEG-LK7@BP stopped the conformational transition and suppressed the fibrillization of A beta(42), so it could completely rescue cultured cells from the toxicity of A beta(42) (by increasing the cell viability from 72 to 100%) at 100 mu g/mL. It is considered that PEG-LK7@BP could bind A beta species by enhanced electrostatic and hydrophobic interactions and thus efficiently alleviated A beta-A beta interactions. Meanwhile, the coupled LK7 on the BP surface formed a high local concentration that enhanced the affinity between the nanosystem and A beta species. Finally, PEG could improve the stability and dispersibility of the nanoplatform to make it show an increased inhibitory effect on the amyloid formation. Hence, this work proved that PEG-LK7@BP is a promising nanosystem for the development of amyloid inhibitors fighting against AD.