Abstract: Based on the relations between the high-overtone bulk acoustic resonant frequency shifts and the changes of the elastic plate thickness, a method for the quantitative measurement of the thickness change of elastic plates was presented. For the harmonic mode with the maximum effective electromechanical coupling factor, the effects of the elastic plate thickness change on the order number of the mode were investigated, and the estimation formulae between frequency shift and thickness change were given. The numerical calculations demonstrated that the method had a high sensitivity of 50 Hz/μm, which could be used to nondestructively evaluate the thickness change and also the surface states of the elastic plates.