The time-resolved EQCM method is described and a theoretical analysis of the relation between the frequency resolution and the sampling rate (time resolution) is presented. It is shown that the time-resolved EQCM can fulfil simultaneously good frequency resolution and time resolution. The kinetics of the oxidation of Ag to Ag2O are studied using this method combined with the potentiostatic technique. The monolayer Ag2O formed at the first stage shows a potential dependent coverage. In the first two stages, the Ag2O layer thickens layer by layer with a rate-determining step of diffusion of Ag+ transients associated with the formation of the bulk phase Ag2O are well consistent with the current transients, and both indicate an instantaneous nucleation and 3D growth mechanism. A relatively accurate method to estimate the mean height h of the cavities at the rough surface is also presented based on the frequency transient and charge density, and a linear increase of h with anodic charge is observed during the potentiostatic process. It has been demonstrated that the time-resolved EQCM can provide valuable information on the transient change of the morphology at the electrode/electrolyte interface.