Triangular silver nanoplates were successfully prepared by a water-bath heating method. NaBH4 and sodium citrate were both used as reducing agents while polyvinylpyrrolidone (PVP) was used as a surfactant and protective agent. The product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, and surface-enhanced Raman scattering (SERS) spectrum. The product has a cubic face-centered Ag structure. The triangular silver nanoplates have a border size of (100±40) nmand a thickness of (10±5) nm. A growth mechanism is proposed to account for the formation of triangular nanoplates. The preferential absorption of citrate on different crystal planes of silver nuclei, the encapsulation function of PVP and the existence of lattice defects in silver crystals plays a significant role in the formation of products. Compared with spherical nanoparticles, the triangular silver nanoplates exhibit a different absorption spectrum and strong SERS activity for pyridine (Py) molecules.