Alzheimer's disease (AD), the most prevalent neurodegenerative disorder globally, progressively impairs patients' cognitive functions and their ability to perform daily living activities. Its core pathologies include β-amyloid (Aβ) deposition, tau hyperphosphorylation, synaptic disruption, and neuroinflammation. Biomarkers such as cerebrospinal fluid Aβ42, T-tau, P-tau, synaptic proteins, neuroinflammatory factors, and dysregulated microRNAs provide critical targets for early diagnosis. However, the invasiveness of traditional cerebrospinal fluid testing limits its application in large-scale screening, giving rise to the development of non-invasive blood biomarker detection technologies. In recent years, biosensing technology based on nanomaterials has become a research hotspot in the field of early AD diagnosis, thanks to its advantages of high sensitivity, specificity, and multi-functional integration. This paper systematically reviews the latest progress of nano-biosensors, such as electrochemical, optical, and surface enhanced Raman scattering (SERS) sensors, in the detection of AD biomarkers. It focuses on exploring the role of nanomaterials in the detection of AD biomarkers.