Alzheimer's disease (AD) is a neurodegenerative disorder with no radical therapy. Aggregation of amyloid β-peptide (Aβ) induced by various factors is associated with pathogenesis of AD. A pyridine amine derivative, 3-bis(pyridin-2-ylmethyl)aminomethyl-5-hydroxybenzyltriphenylphosphonium bromide (PAT), is synthesized. The inhibition of self- and metal-induced Aβ aggregation by PAT is confirmed by thioflavine T fluorescence, circular dichroism spectroscopy, and TEM. Western blot, RT-PCR and fluorescence imaging indicate that PAT can alleviate the Aβ-induced paralysis, reduce the production of ROS, and protect the mitochondrial function in transgenic C. elegans. Genetic analyses indicate that heat shock protein is involved in the alleviation of Aβ toxicity. PAT also inhibits the activity of acetylcholinesterase in C. elegans. Morris water maze test shows that the memory and cognitive ability of APP/PS1 AD model mice are significantly improved by PAT. Both in vitro and in vivo studies demonstrate that PAT is effective in counteracting Aβ toxicity and ameliorating cognitive functions in AD mice, and therefore a potential lead compound of anti-AD drugs.