The invention relates to a high-sensitivity transformer winding loosening determination method, and belongs to the technical field of power transformer safety monitoring. The method involves executing the following steps: 1, installing a plurality of vibration sensors for a frequency band transformer; 2, obtaining reference vibration signals of the frequency band vibration sensors; 3, taking the characteristic frequency band scope amount of the reference vibration signals with noise being eliminated as a reference value of the frequency band transformer; 4, determining whether the frequency band transformer already has a reference value, if so, going to step five, and otherwise, going to step one; 5, acquiring vibration signals of the frequency band vibration sensors; and 5, comparing the characteristic frequency band scope amount of the vibration signals with noise being eliminated with the reference value so as to determine whether the winding of a frequency band transformer is loosened. According to the invention, analyzing is carried out by use of the vibration signals generated when the transformer is closed in case of a zero load, and whether the winding is loosened is determined by use of excitation inrush currents generated in a line in case of the zero-load closing, such that winding loosening detection sensitivity is improved.