Parts of compounds, after being labeled by radionuclide, of the phenyl benzyl ether derivative, are used as Aβ plaque imaging agent. The structural formula of the phenyl benzyl ether derivative is shown by formula (I). The present invention develops a kind of brand new phenyl benzyl ether derivative which has high affinity with Aβ plaques in brains of AD patients. The chemical structure of the phenyl benzyl ether derivative is different from that of compounds disclosed in the prior art and the phenyl benzyl ether derivative belongs to a brand new compound for diagnosing and treating AD. The obtained Aβ plaque imaging agent has the advantages that the in-vivo stability is good, the fat solubility is low, the removal speed for the brain is fast, the problem of removing the radionuclide in vivo does not exist, and the application prospect and the market value are great.