The electrochemical quartz crystal microbalance (EQCM) is used to investigate the characteristics of the thiolated self-assembled monolayer(SAM) on gold surface.A 5MHz QCM element serves as both the mass-sensitive sensor and the working electrode of the electrochemical system.The 6-mecapto-1-hexanol and and the 16-mer oligonucleotide with a mercaptohexyl group at the 5’-phosphate end are utilized to form the SAM on the gold electrode.The frequency response of the QCM during cyclic voltammetry (CV) scanning and cbronoamperometry are recorded together with the electrochemical current.The experimental results indicates that the frequency response is more sensitive to the surface coverage.Therefore,the response of the EQCM reveals more details of the SAM on gold electrode.It is especially useful for analysing the immobilization quality,such as probe orientation and coverage,of the SAM. The electrochemical quartz crystal microbalance (EQCM) is used to investigate the characteristics of the thiolated self-assembled monolayer (SAM) on gold surface. A 5MHz QCM element serves as both the mass-sensitive sensor and the working electrode of the electrochemical system. 6-mecapto-1-hexanol and and the 16-mer oligonucleotide with a mercaptohexyl group at the 5’-phosphate end are utilized to form the SAM on the gold electrode. Frequency frequency of the QCM during cyclic voltammetry (CV) scanning and cbronoamperometry are recorded together with the electrochemical current. The experimental results indicates that the frequency response is more sensitive to the surface coverage. Beforefore, the response of the EQCM reveals more details of the SAM on gold electrode. It is particularly useful for analysing the immobilization quality, such as probe orientation and coverage, of the SAM.