Omega-mercaptohexanoic acid (6-MHA) self-assemble-modified gold electrode has been made by the authors. The SERS spectrum and the variations of double-layer capacitance (Cd) which occurred in the formation of 6-MHA self-assembled monolayers (SAM) on gold electrode surface were studied. The structure model of this SAM was deduced. The results show that 6-MHA can form stable SAM on gold electrode, and this 6-MHA SAM electrode has obvious catalysis for the redox reaction of chlorophylls.