U nder the excitation of harmonic wave, the vibration characteristics of power transformer core show different characteristics compared with the working conditions. In this paper, the experimental transformer is taken as the experimental measurement object, and an iron core vibration measurement platform with adjustable harmonic excitation is built. Then we measured the surface vibration of the iron core under different harmonic excitation. The spatial distribution characteristics of the surface vibration of the iron core under different harmonic excitation are analyzed. Compared with the experimental mode analysis of the iron core, the results show that the existence of harmonic excitation can greatly increase the vibration of the iron core and stimulate more vibration modes of the structure. The research in this paper can provide reference for the modeling of core vibration under harmonic excitation.