Graphene oxide (GO)/Ag nanoparticle (NP) hybrids are obtained by in situ reduction of Ag NPs on GO sheets. In this letter, the influence of the conformation of GO sheets on the surface-enhanced Raman scattering (SERS) effect of GO/Ag NPs is investigated by covalently grafting folic acid (FA) molecules onto graphite sheets. SERS measurements are conducted in aqueous solutions with different pH values. Data show that the SERS signals of FA are pH dependent, consistent with the morphological changes of GO sheets.