Background:　Surface-enhanced　Raman　scattering　(SERS)　has　become　a　useful　spectroscopic　tool　for　studying　biomolecule　structures.　The　main　types　of　plasmonic　substrates　used　in　biological　systems　are　Au　nanoparticles　(AuNPs),　whose　surface　plasmon　resonance　depends　on　the　nanoparticle　size,　morphology,　particle　interspace,　and　so　on.　Methods:　In　this　study,　AuNP　colloids　with　different　sizes　were　synthesized　and　used　as　the　sensors　to　probe　SERS　signals　of　different　biomarkers　and　biomolecules.　Results:　The　results　showed　that　an　AuNP　colloid　of　similar　to　50　nm　had　excellent　SERS　effects　in　probing　various　molecules,　and　could　be　preserved　for　about　3　months　with　excellent　repeatability　and　reproducibility　(RSD　＜5%)　in　terms　of　the　probed　signal　intensity　(rhodamine　6G　and　crystal　violet).　Meanwhile,　the　fabricated　AuNPs　were　applied　to　study　the　SERS　signals　and　structural　information　of　bovine　serum　albumin　(BSA)　in　aqueous　solution.　It　was　found　that　SERS　could　rapidly　provide　the　structural　information　and　vibration　characteristics　of　BSA.　Conclusion:　It　was　concluded　that　biocompatible　AuNP　colloid　may　be　a　promising　biosensor　in　the　rapid　and　label-free　detection　of　biological　systems.