EQCM can be used to monitor the chemical reaction occurring on the electrode, which offers the optimized reaction condition by comparing the influence factors during the synthesis process. Some previous work has already investigated the polymerization process and charge transport properties, polymer film growth on gold electrode surface, and polymerization process of polypyrrole and its derivatives. EQCM was used to study electro-polymerization process and doping/de-doping properties of polyaniline film on gold electrode surface as well. To investigate the electrosynthesis process, sometimes it is necessary to combine other characterization technologies, such as using FTIR and EQCM to study the effect of different conditions on the formation of poly(3,4-ethylenedioxythiophene) film structure, and using EQCM, together with AFM, FTIR, EIS, to investigate the film formation process in the alkyl carbonate/lithium salt electrolyte solution on precious metal electrodes surfaces.