In this paper, gold nanoparticles with branches were prepared in aqueous solutions using seed-mediated growth method. The mean diameter of the seeds chosen for these studies is 6~8nm. The influence of reducing agent used in synthesis gold sphere as seeds was investigated. A reaction mechanism of fabrication gold nanostar particles was systematically described. The nanoparticles synthesized were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. In order to investigate their optical property, Surface Enhanced Raman Scattering (SERS) spectrums were tested, which showed quite good Raman enhencement.