A simple physical approach to prepare gold (Au) nanoparticles with sharp edges for increasing surface-enhanced Raman scattering (SERS) response is presented. The shape evolution process of Au nanoparticles under different fabrication conditions is studied, and a thermodynamic model is adopted to explain the shape transition. Single-crystalline Au nanoprisms with regular hexagonal shape can be formed at a certain annealing temperature. Coating of these Au nanoprisms with graphene causes them to exhibit a SERS enhancement of 60x. This is the fi rst demonstration of a physical approach to fabricate regular hexagonal Au nanoprisms that exhibit an ultrasensitive SERS effect. Furthermore, the local fi eld distribution of a series of Au nanoprisms with different sizes is simulated to better understand their ultrasensitive SERS performance.