Novel gold nanoparticles (GNPs) as a SERS probe were prepared using two types of functional PEG/oligoamine polymers possessing biotin as biotag molecules at the PEG end or a coumarin moiety as a Raman probe molecule between the PEG and oligoamine segments. Eventually, the GNPs showed excellent dispersion stability under physiological conditions, as well as remarkable SERS signal resulting from molecular recognition between streptavidin and the biotin tag, even in the presence of bovine serum albumin (BSA).