The method of monitoring the tank vibration is becoming an effective method to detect the winding deformation of power transformer for the reliable and secure operation of power system. In order to further identify the relationship between the winding deformation fault of power transformer and the measured tank vibration signals, the short-circuit test is done in a 220kV transformer with the developed vibration measurement system and the vibration frequency response curves for some pre-setting winding deformation faults are obtained. Multi-fractal spectrum is applied to analyze the of the obtained vibration signals when winding conditions of power transformer are changed. It is shown that multi-fractal spectrum can effectively indicate the geometric structure features of vibration signals. The parameter variations of multi-fractal spectrum are agreed well with the preset winding faults, which provides another method for the feature extraction of vibration signal to detect the winding deformation of power transformer.