A novel solid substrate with high surface-enhanced Raman scattering activity was fabricated by preaggregated colloidal silver nanoparticles. The effect of preaggregation degree on the SERS activity of the substrate was studied by UV-Vis spectroscopy, TEM and SEM. It was found that the SERS activity was directly dependent on the preaggregation degree. This kind of substrate can be used as a highly sensitive SERS substrate with many advantages such as uniform nanoparticle distribution, homogeneous SERS activity, and wonderful enhancement effect. The excellent SERS activity of the substrate was proved by the distinct SERS spectra of Rhodamine 6G, 3-mercaptopropionic acid and 9-aminoaceridine hydrochloride monohydrate.