The invention provides a method and a system for detecting the deformation of a transformer winding. The method comprises: acquiring response end voltage and exciting end voltage of the transformer winding to be detected under different frequency; calculating a transfer function module value of the transformer winding to be detected according to the response end voltage and the exciting end voltage; drawing a frequency response curve in a coordinate system according to the transfer function module value under different frequency, and drawing a frequency response curve in the coordinate system when the transformer winding is normal; pre-processing the two frequency response curves by using an erosion method to obtain curve data satisfying a preset condition, and calculating relevant coefficients of the two frequency response curves; and judging the deformation condition of the transformer winding to be detected according to the magnitude of the relevant coefficients and relevant coefficient preset values. According to the method, the two frequency response curves drawn in the coordinate system are pre-processed by using the erosion method, so that burrs are removed, interference of noise such as electromagnetic signals and the like is avoided, the accuracy of diagnosis is improved, and the probability of misjudgment is reduced.