This review concentrates on AuNPs due to their superb properties. AuNPs have been known since ancient times as colloid gold and employed in many applications. AuNPs can be synthesized in a various forms and sizes using different chemical methods. Typically, precious metals, including not only Au, but also Pt, Pd and Ag, are resistant to oxidation reactions and so they are selected to be the working electrode in electrochemical systems. Au or AuNPs are the most frequently chosen of the precious metals for electrochemical systems due to the relatively low cost and ease of preparation. The AuNPs can be stabilized by negatively charged anions around the surface making it easily modified by a wide range of biomolecules bearing a thiol moiety. The use of AuNP to enhance detection sensitivity is reviewed as follows.