DC bias will aggravate the transformer vibration. Usually, a simplified model is used to calculate the winding vibration to simplify the winding to a cylindrical model that ignores the block structure. Although it saves the calculation time, it makes the calculation result have a large error from the real situation. This paper establishes a refined model of wire-pie-type windings including pads. Based on the analysis of the excitation characteristics of the transformer under DC bias, through the coupling of electromagnetic field, structure field, and fluid field with multiple physical fields, The vibration displacement characteristics are studied and experimentally verified. The results show that the magnetic flux leakage of the transformer increases under the DC bias, and the distribution is concentrated at a specific angle. A new unilateral vibration mode appears at the corresponding position of the winding. The imbalance in the local displacement of the winding increases the possibility of the pad falling off, and the anti-burst ability of the transformer decreases. . This research can provide theoretical guidance for fault monitoring of DC bias operation.