Abstract: Transformer is the core equipment of voltage conversion and power transmission in power system. Its safe and stable operation directly determines the quality and reliability of power supply. As the core component of electromagnetic conversion, winding faults are high and harmful. The integrity of its structure directly affects the operation performance of the transformer, which is the main hidden danger restricting the service life of the equipment and the safety of the power grid. In order to study the vibro-acoustic characteristics of transformer winding when it is loose, this paper proposes a research method of vibro-acoustic characteristics of transformer winding based on multi-physical field coupling simulation. According to the test model, the transformer winding model is established in the simulation software. By changing the pre-tightening force of the upper and lower ends of the winding to simulate the degree of winding looseness, the vibration signal of the winding under different pre-tightening forces and the voiceprint signal of the surrounding environment are obtained. During normal operation, the main frequency of winding vibration acceleration is 100 Hz, and the main frequency of ambient sound signal is 100 Hz and 200 Hz. With the decrease of preload, the main frequency of winding vibration acceleration increases from 100 Hz to 150 Hz, the proportion of 100 Hz component of voiceprint signal increases, and the frequency of high frequency component decreases by 5 ~ 10 Hz. Finally, the effectiveness of the simulation method is verified by comparing the measured and simulated data through the real transformer test. This study clarifies the correlation between the degree of winding looseness and voiceprint signal and vibration signal, and provides a basis for the evaluation and prediction of transformer winding state.