Alzheimer’s disease (AD) is the most common form of irreversible dementia. In addition to assessing of patients’ memory abilities, positron emission tomography (PET), as a non-invasive diagnostic modality with high sensitivity and qualitative or quantitative imaging of the target sites, can qualitatively and quantitatively evaluate β-amyloid (Aβ), tau proteins, synaptic proteins, and other related biomarkers, which is of great significance in the diagnosis of AD. As PET imaging approved by FDA, [¹⁸F]-flutemetamol, a derivative of ¹⁸F labelled thioflavin-T, and [¹⁸F]-florbetaben, [¹⁸F]-florbetapir, which are phenylpyridine derivates, have high specificity in their affinity for Aβ plaque binding. Other radionuclides such as ⁶⁸Ga and ⁶⁴Cu labeled radiotracers also showed high affinity with Aβ plaques. Quinoline derivatives [¹⁸F]-THK5351, [¹⁸F]-PPQ8, benzimidazolopyrimidine and pyridine-indole derivatives [¹⁸F]-T807, and lansoprazole derivatives [¹¹C]-NML as PET imaging agents, can quantify tau protein tangles. And the structural derivatives of levetiracetam [¹¹C]-UCB-J and [¹⁸F]-SDM-8 can measure synaptic density, while the structural derivatives [¹⁸F]-FPEB of 3-fluoro-4-acetylidene-benzylnitrile can assist in the diagnosis of AD by binding with mGluR5. The fluorobenzoyl derivative [¹⁸F]-altanserin, with ketoserin as its structural parent, acts on 5-hydroxytryptamine to study the molecular changes of early AD.