Graphene oxide (GO), an oxidized form of graphene, holds a similar single-atom-thick structure to graphene, but possesses plenty of oxygen -containing functional groups, such as carboxyls on the edges and hydroxyls and epoxies on the basal plane. GO possesses extraordinary properties, including low cost manufacturing, rich colloidal properties, high adsorption, and strong fluorescence quenching. GO has also recently been demonstrated to have advantageous applications in the biomedical field and in biosensing. Nevertheless, one critical question needs to be addressed before any actual applications can be discussed: how does GO interact with biomolecules? In this chapter, we will approach this question and briefly summarize the recent progress from the views of surface chemistry and spectroscopy methodology.