Spherical α-Fe2O3/Ag core/shell nanoparticles were prepared by reducing Ag(NH3)2+ with formaldehyde using the seeding method. 3- Aminopropyltriethoxysilane (APS) acts as a “bridge” to link between α-Fe2O3 core and Ag shell. The obtained nanoparticles were characterized by XRD, TEM, SEM, EDS, and Roman. The results show thatα-Fe2O3 cores are coated by Ag shell completely. The average size of α-Fe2O3/Ag nanoparticles is 95 nm and the thicknesses of Ag shell are 15nm in 3.7% HCHO and 1.0M AgNO3. The thickness of Ag shell can be tunable by changing reaction conditions, such as the concentration of AgNO3, reduction reaction rate. The surface-enhanced Raman scattering (SERS) effect of the core/shell particles are measured with Pyridine (Py) as molecule probe. SERS indicate that the Raman signals of Py adsorbed on α-Fe2O3/Ag nanoparticles exhibit large enhancement at 1010 and 1038 cm-1 respectively. And the intensity of signals is enhanced with the increase of the thickness of Ag shell. The uniform and rough surface of α-Fe2O3/Ag particles exhibits strong SERS activity in 3.7% HCHO and 1.0M AgNO3. The spherical α-Fe2O3/Ag core/shell nanoparticles exhibit SERS activity.