In view of the difficulty in distinguishing the core fault from the winding fault due to the connection of the mechanical structure of the transformer core and winding, a method based on vibration signal is proposed to distinguish the core fault from the winding fault. By comparing and analyzing the non-linear characteristics of magnetostriction of ferromagnetic materials and elastic deformation of insulating pads, the vibration signals of the transformer core and winding are obtained through experiments. The non-linear characteristics of vibration signals of transformer cores and windings are studied in frequency domain. By analyzing the proportion of high-order harmonic energy of vibration signals under different conditions, it is proposed that the core fault and winding fault can be distinguished by the variation law of fundamental frequency and high-order harmonic amplitude of vibration signals. The research shows that the fundamental frequency component of vibration signal in transformer operation is determined by the vibration of core and winding, and the high-order harmonic component mainly comes from the vibration of core. When transformer winding faults occur, only the fundamental frequency amplitude of vibration signal increases sharply; when core faults occur, both the fundamental frequency and the high-order harmonic components increase sharply, which can effectively distinguish core and winding faults.