Vibration signal on the surface of transformer is closely related to the running condition of winding and core. Three-dimensional vibration signals on the surface of normal running transformer are measured. Combined with the data of load current and operating voltage, the peak characteristics in time domain and the energy characteristics in frequency domain of vibration signals on the surface of transformer in different directions are analyzed and summarized. In order to quantify the energy at each frequency influenced by the change of load current, the index of energy-load current sensitivity (EC-S) is proposed, and the characteristic frequencies representing the vibration state of the winding are analyzed. The results show that the vibration signals on the surface of transformer have significant differences in different directions on the same position, and three-dimensional vibration signals are more comprehensive than single direction vibration signal in reflecting the vibration changes of the transformer winding.