Abstract: With facile electrochemical deposition method makes a new and unique dendritic silver nanostructure consist of trunk，branch and leaves. Adopts scaning electronic microscopy（SEM）and X-ray diffraction（XRD）to characterize the structure of silver nanostructure，combined with the structure feature to explore the formation mechanism of dendritic silver nanostructure，the dendritic nano silver has very strong symmetric construction. The unimolecule determination experiment show：because of the structure features of high aspect ratio，numerous interstital structure，single crystal leave shape silver with nano-size，the prepared dendritic silver nanostructure has excellent SERS（surface enhanced Raman Scattering）activity as SEMS substrate，it can be used for ultralow concentration unimolecule determination.

Key words: surface enhanced Raman scattering, hierarchy structure, silver nanostructure