Abstract: The paper mainly focuses on the study of the vibration principle and noise spectrum characteristics of transformer bodies, and on the establishment of the relevance of magnetostriction, vibration transmitting path, tank vibration and the external noise characteristics of oil tanks. An introduction is made on the mismatching problems between the existing equipment standards and noise emission standards. The vibration accelerations of cores are measured in two directions to determine the frequency characteristics of vibration. The sound pressure level characteristics, frequency spectrum characteristics, vibration characteristics and their concentration of power transformers are discussed based on a comprehensive analysis of numerous measured noise data of substations. The correlation between the magnetostriction frequency and the external noise characteristics of oil tank is established, and it is proved that the noise frequencies are mostly 100 Hz or its integer times. The vibration frequency of transformer core caused by magnetostriction is two times the frequency of power frequency exciting current, which is equal to 100 Hz. The external noise of oil tank is characterized by that both the fundamental frequency of 100 Hz and the higher harmonic frequency of its integer times such as 200 Hz, 300 Hz and 400 Hz have remarkable peak values. It will be the focus in the future to develop the technology for noise reduction of the transformer bodies.