In order to overcome the shortcoming of excessive attenuation of high-frequency components of traditional pulse frequency response method in detecting the deformation of power transformer winding, a new method of obtaining the frequency response curve of the transformer winding based on the sinc signal is proposed. The frequency characteristics of the sinc signal and the pulse signal were compared theoretically, and the advantage of the sinc signal was explained. Finally, the tests of the customized transformer winding in the laboratory were carried out by using the sinc signal and the pulse signal respectively, and the detection results of the two signals were compared by the correlation coefficient. The experimental results show that the frequency response curve of stable and wide frequency domain can be obtained by using sinc signal as the excitation source, and the detection result of this method is more accurate than that of traditional pulse frequency response method.